I did quite a bit of research on trying to find anything that listed frame interchangeability, the closest thing I could find was a description of the changes made to the frames over the years listed in the book "How to Rebuild your Corvette Rolling Chassis 1963-1982" on page 54. In general when the bumpers changed fom chrome to plastic the mounting points on the frames changed as well. But gas tank mounts, cross member, exhaust routing and body mount heights all changed over the years as well so you have to be careful. If you do a Google search on that book the text will come up and you can read it. I also found this link helpful:
http://www.71corvette.com/frames.html
Finally, if you look at the web sites of frame resellers they will group the frames into the years that are interchangeable so that will give you more info. So far the best deal I could find for a 72 frame is a guy who is at Carlisle every year selling refurbished frames, don't have his contact handy but if you are interested I can look for it. Good luck!
PS I did not get a reply form vettsteve either so I'd like to know if he is still out there too.
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Mario