'UGH!' describes my 66 GS vert project too! It's a metal working challenge but it's coming along piece by piece.
I did the inner fender repair too. Made templates from cereal boxes, made the metal parts, and TIG welded in place. The tig is nice as it leaves a fine bead that is easy to finish off.
I went with the one piece trunk for this job. Cost more but it's a very nice piece.
I bought a 66-7 Chevelle trunk drop off to try, but it's way off. Olds and Pontiac are also much different. I have a pair of decent used ones, or may try to duplicate them.... a $100 bead roller is a handy tool for fabbing parts, as is the shrinker/stretcher set.