I am also interested in hearing what others have to say about this. I am a long way from getting to this point, but have been contemplating how to make my jig as I continue stripping the car down. The whole underside of my car is coming off, but the rockers actually seem in pretty good shape and all of the gaps seem pretty good right now.
Hopefully I will continue to gain more understanding and enlightenment as I disassemble everything. But from my initial research, it looks like the rockers should run parallel to the datum line and the front frame rail to radiator support is slightly inclined from firewall to radiator.
I plan to use the "whole floor assembly", core support, strut braces, etc... I am going to order everything and have it on hand BEFORE I start taking anything out. I am just starting to develop a plan for some type of jig to keep the body in position and sliding the floor assembly underneath. Or more correctly, I will probably use my lift to position the body on top of the floor assembly. Lots of thoughts in my head, but no real plan yet.
Looking forward to hear how this pans out.
67 390 Coupe C6, PS, PB, AC (SJ built 1/4/1967)
67 390 Fastback C6, PS, PB, AC, Tilt (Dearborn 3/5/1967)
07 Vert 40th Anniv Shelby GT500