I'll email you the frame diagrams- the mounts you're referring to are just rest pads for the body- no bolts...on convertibles/station wagons, they did get bolted down. theres one more set behind rear wheels that are just pads also- I believe they did this just to make the ride quieter, and dont know if it would be better or not to bolt to all of them. In looking at it, it would seem that if you bolted them all, you might need to come up with a way to measure deformation of mounts more than bolt torque due to different diameter donuts...perhaps a bunch of mag base dial indicators from frame to body could be used to do one side at a time and get even deformation as each is tightened- but if glass is in body this would have to be done in many small steps to prevent twisting anything...just a thought.
You might want to email Russ Owens(firstname.lastname@example.org) thats done a lot of frame transplants, to get his thoughts on full mounting of hardtop bodies- I emailed him before about something on mine, he has a lot of experience on these things...heres a link to his webpage:
If I had to do it all over again, I think I would have removed the glass (on a warm day so adhesive will be soft)before bolting everything down, just in case...I really think mine was already in a slight bind due to sitting on a soft frame for years- then removing rear window trim relieved enough support from the glass to cause it to explode a day after. Surely I aggravated the problem by mixing rubber and urethane mounts- live and learn I guess.
I wouldnt worry too much about the bigblock- these things had 427's available, and I havent ever read anything about structural problems other than the rust issues...unless you plan on putting slicks on it with a steep rearend, I really doubt youd be able to hurt it.
Goodluck- put some pics up if you get a chance : )