...without a jig.

I am splicing in the right front headlight box, forward section of the inner fender, and the vertical brace. I am keeping the original floor, and the semi-original front panel, which got pretty banged up.

My approach has been to get the straight splice section located properly, and then use that as a guide to work the end of the front panel into proper shape.

I have been measuring distances between as many reference points as possible, and comparing the right side to the unmolested left side. At this point I have a pretty good match, referencing spots like the upper edges of the headlight box, the headlight pivot hardware mounting points, corners on the brace, etc. relative to the gas tank bulkhead upper edge and front panel. I have also measured and compared angles. And I propped the front hood in place, and compared to that. At this point, I have everything within a 1/16 inch and 1 degree.

Anything else to consider or measure?

1/16" is well within factory tolerances. 1/16" is approximatley 1.5mm. There is no way the factory was +/- 1.5mm back in the 70's.

Just be sure to weld very slowly. weld, cool, alternate between ends of a given panel . . . . repeat endlessly. You don't want to weld up a big section and get warping and shrink when it all cools.