Just take it all apart and figure it out as you go lol Best way to do it...only way to learn it
Now that I still haven't put my 402 in my '72 Blazer, I'm just going to do a frame off this month and next I think and redo the entire body etc properly. I figure may as well and shouldn't take too long....even though we all know they do.
Good luck with the tear done and rebuild. Get some pics up of the beast as you go along.