Greg72,
Thanks for your comments. I concur with bringing the K5 back to life. I bought the ’71 over ten years ago knowing full well it had a lot of rot. (Hell, it was that baby-scheisse ocher yellow on top of it all). I had every intention of trashing the body and using the chassis & drive train to swap under my ’49 Willys wagon. As it turned out, the damn Blazer had a soul of it’s own and my wife wouldn’t let me chop it up. (First restoration trick… let her think it’s her ride you’re restoring). Granted, if you drove it through a water puddle, you’d get splashed in the face… but as reliable as your favorite hunting dog. Good karma. It deserves a new lease on life.
I think you’ve got the right idea on the welding. I use a MIG (170 amp / 220 volt). It doesn’t take a lot of $$ to get a decent MIG welder. I bought the 170/220 because, ironically, it provides better control at lower settings.
Spend the money and purchase an auto-darkening helmet (speed glass) and it will make you an instant expert.
TIG is a far superior welding process when it comes to the quality of the weld, but MIG is the only way to go for the occasional home hobby guy (i.e.; me). When you butt weld with TIG, you butt the two pieces right up to each other. With MIG, you need to leave a gap about the width of the material thickness. One disadvantage to MIG is the grinding involved in the finish work. Grinding warps the metal, but with practice you can minimize the bead.
Buy a book and read all about it before you get started… and then throw it away because it’s all practice. The most important consideration when doing the bodywork (i.e.; patch panels) is to keep the heat down by joining the metal with a series of tack welds. If you try to run a long bead on sheet metal it will warp it to hell. Keep the tacks as far apart as possible and let the metal cool all the way down. Take your time and fill in the seam by alternating the tack welds in between.
On my tub, for the factory assembly points such as the rockers and floors, etc., I used the factory assembly manual to reference the spot-weld placements. You really can’t tell the thing was chopped to pieces, even from the backside / underneath… and the spot welds look factory. Another trick is to select your patch areas carefully. I made my cuts near the style lines (a trick learned from a veteran body man) to provide a little more strength and stability against metal warping and shrinkage.
When you are fabricating the complicated stuff, mock it up in cardboard first. Some of my favorite body tools are the body saw, air cutter, snips and air grinder but God I wish I had a plasma cutter. Next year.
Last word of advice that can’t be overstated… don’t cut anything until you have in your possession and have studied closely the replacement piece. The quality of the off-the-shelf replacement panels suck. I returned a lot of stuff before I was satisfied with what I had to work with. A lot of times, the ‘yard is the only place to go for good body parts or partial clips.
Hope this helps. Go for it and have fun in the doing!