I did mine a couple years ago, and here's the basics: first I carefully cut out the indentation where the '68 reflectors went. I used a die grinder with a cutoff wheel and took my time. Then I filed the opening to get it nice, then used some sheetmetal that was slightly thicker than the original '68 sheetmetal to fill the opening. I simply held the sheetmetal inside the trunk opening and traced the shape with a felt tip pen. Then cut the new metal to shape, and be sure to take the time to get it perfect. I used a woodworkers profile gauge to get the compound curve right on the outside. Then I mig-welded the piece in, but you can't just start laying a bead. I taped the patch in place and tacked it in about four places. Then I removed the tape and rechecked my contour. Welding shrinks the metal around the tack, so you need to "adjust" this as you go. Do this by using a body hammer and dolly (please don't be tempted to use a ball peen hammer and a brick) and hit the tack weld ONLY! The idea is to use the hammer on one side and the dolly on the other side of the tack and hit the weld hard enough (three or four good solid hits should do it) to actually "relax" the metal by stretching it out. Once you hit directly on each weld a few times (assuming you didn't break your weld) then move on to four more solid tacks and repeat the hammering process each time. Try to do this while the tack is still hot, but if it cools don't worry. Keep feeling the panel around the area your working on and anytime you can't hold your hand close to the spot your welding, stop, you'r getting the panel too hot and risking warpage. After all the tack welds touch, you're about done. LIGHTLY grind the weld down (I use flapper discs on my 4" grinder) being careful not to touch the patch or the original panel. You may find you need to weld a couple more spots at this time. Once you've got the weld almost flush with the panel, use some 80 grit on a block and sand in an "X" pattern across the bare metal patch. Anywhere your paper isn't touching is a low spot. Try tapping it up from the inside but don't get too carried away, just get it close enough for filler. I try to keep my filler at 1/16", but realistically, you could go a bit deeper with no problem. Just make sure to keep an eye on your shape, I use a straight edge to find the highs and lows. It's not that hard, I've got some pics of mine around here somewhere, let me know if you want to see them and I'll try to dig them out and post them.
