One of my biggest regrets from my childhood is -
I never learned to weld.
I guess my family was too busy getting me a conventional education full of reading, writing, mathematics and the like. We were middle-class, never hungry but no big vacations, and were too busy getting on with things to take care of the really important education. Lucky for me, my Guru taught me what can be done with a $90 welder.
Welding is great! Steel is great. Nuts, bolts, screws, rivets, they're all great too, but nothing beats taking two pieces of steel and melting them into one piece.
VW knew this, and they welded lots of neat stuff. They also had an assembly line to deal with, so they didn't weld enough for the baja!
Following is a list of things that one ought to consider welding. You'll recognize them when you see them - two pieces of steel, would be stronger if they were one, you get the idea.
Also included is a bit on where to put gussets. By gusset, I mean a piece of steel over a weld, welded on itself, to make the welded section 3 times as strong. One could consider gusseting everything mentioned, but that would be a bit much, and some of the pieces mentioned - well, once welded, when they break, they break. Endo story.
The front end has the two vertical mounts on the end with the shock mounts on top. You can make this substantially stronger by welding a bead along the edge of said towers. During a really bad twist, these sections might try to separate. If welded, the twist won't be as bad.
Straight and simple, but noteworthy!
Similar to the front end towers, the rear frame horns (stretching out below the transmission) were fabricated as two separate pieces. Here again, to weld the edges will keep them from bending so easily.
OK, it's durn hard to bend 'em, but I've done it, and I've seen a number of repaired frame horns, so I ain't the only one. Another fact worth mentioning is, if a rear carriage bolt is lost (these hold the transmission cradle to said frame horns) on a '69 or later model, the CV joint will chew a hole into the frame horn.
This is a time for gusseting. Weld the hole as best as possible, then take one piece of, possibly, 3" by 4" 3/16" thick metal and bend it to shape. I recommend the concrete curb in front of the neighbor's house - great bending surface. Hit said steel with BFH to get an approximate bend or three. Weld this little sheet of steel over the hole, one surface at a time. Hit the steel with hammer and possibly a drift, to form-fit it a bit closer, and weld another edge. Hammer, weld. It makes a close fit (assuming you hit it hard enough) and won't interfere with any clearances, but it makes the strength triple!
You aren't going to believe this, but after you've broken a nosecone or three, the mount that the nosecone bolts to is suspect to break loose from the body of the car. What to say? It's factory stuff, probably 30 years old or better, and would've lasted forever on a street sedan with a 40-horsepower motor.
Assuming you catch it in time, simply lay a monster bead over the existing weld, inside and out. If you wait too long and it breaks, you'll need to gusset said weld. a 2" by 2 1/2" sheet of steel will bend nicely and hammer into place. This is a simple L-shape, the neighbors won't even notice that little bit of hammering on their curb.
If you're wise, good and tall, you have front end adjusters. These had to be welded in.
Given this, if you don't have extremely heavy steel protecting your front beam, better gusset said adjusters. The bad rock on the other side of the small dip will catch your diving front end and break the lower beam in two!
This is a simple one, 3" by 4" sheet steel bent as you go. Fun with BF hammers!
The part of the body near the rear shock mounts (top) likes to c rack. Once cracked, it procedes to split all the way across the wheel well, make terrible noises and let wind through your car. Not a Good Thing.
I'd recommend a weld around said mount before this happens. It's accessible through the wheel wells, and the rear portion of said mount is more vunerable than the front.
If you wait too long, you have the noble problem of welding thin sheet metal. I tried and slagged big holes. Stank bad when I started the interior on fire. I bought a professional weld for $25 and problem solved, but I had to explain the lousy welding away - durn that friend of mine, the fool told me he could weld that... how embarassing....
The Guru actually wanted me to list this as "redo the whole pan with serious sheet metal" but I'm not ready to go there. The cost is prohibitive, the welding is extensive and cutting alone will take a day. I have some nice dings on my pan, but nothing to keep the girls from riding along (granted, I hammered on 'em already) thusly, the pan has some give, wait for real repairs before investing in serious sheet.
Regarding the battery pan, it is different - it has battery acid all over it. In those salty climes it rusts out readily. Cut it, weld in a serious sheet. Or don't cut it, weld in a sheet anyway, when it rusts out you'll weld in another sheet. for a 28" by 18" sheet you are not losing any sleep over the cost.
As soon as I mention this, everyone's gonna want to know the exact measurements of the cuts? I'm not prepared at this time but I'll get 'em if possible.
Root problem is a common one, over 20 years or so the clutch cable worked a million times, and eventually the weld(s) that hold the clutch tube into place break. Clutch adjustment becomes a real pain in the @#$ and you have to tighten too much to get too little clutch action.
LISTEN to the problem. The break is either in the front, or in the middle. (The rear seldom breaks.) Once isolated, cut a hole in the center tunnel of your car and weld the tube back into place. Consider reinforcing with a 10" bolt run through the tunnel - this'll help prevent at least one direction of stress before it breaks next time.
Rough estimates: Behind the passenger seat rail, 4" behind the pedal assembly. In the front you can see it. In the middle, cut a section out of the side.
YOU MUST RE-WELD THESE CUTS. They are major frame members and even though they're the handiest little access tunnels you've ever wanted, Close Em UP! If your pan ever buckled you'd be cussing extremely loud.
So you're a big boy - you have a roll bar. It's bolted in, with good bolts yet flexible bolts.
Try this: Weld a bar from the rear frame horns (ground to fit to contour, of course) then weld to another plate that bolts to the bottom of the pan, same bolts as the rear rollbar mounts. Make sense? bolts hold frame members in place? hmmmmm
It's important that one learn the art of welding two pieces of steel with different thicknesses together.
It's also a crime when you can't get the top off of a bottle of premium beer, so weld a bottle opener to your front bumper and cover all bases!
Do not weld in your rollbar. You want the rollbar to be bolted to the pan, bolted together with strong bolts that bend and don't break. Should you need the rollbar in a big way, it'll be there for you. Should you want to remove the rollbar, that works too.