You have quite the job coming your way. If you are an experienced welder then go for it. If not, consider Chief's recommendations.
You can verify your panel placement using the dimensions give in the Fisher body book.
On my 68 vert ... I replaced my entire floor pan (except trunk floor), patched rockers, replaced rear quarters, rear wheel wells, patched front cowls, replaced dash top panel, patched toe kicks. I got the frame straightened and then measured the car based on the nos. in the Fisher body book. It was very close and probably better than stock. I installed all body panels for a fitting fit test and everything aligned well without much fuss.
It's a fairly simple process to verify measurements that can be done by one person.
