Ken - here's the link to an old discussion that
had some bits about the 914 as a basis:
914 stuff
The main issue you have already touched on. How much of
the unibody would you have to chop up (and at the expense
of structural integrity, safety, and stability) is a major
problem.
John Stone has been working on a Pantera based GT40,
and had to deal with the same issue of hacking up the
unibody frame to fit the GT40 stuff, and then reinforce
what was left. Some info here:
John Stone Pantera
I'd love to check out your FFR sometime.
Ian