Well, the car is the same, but the suspension is not. The 6's had 4 lug wheels and weaker suspension components. V8's had 5 lug wheels and a beefier suspension, so you would want to make sure you did it right and swap everything. As for the size of the motor, 64-66 you are better off sticking with a small block as you will have to make Shock tower mods to get a bib block to fit. 67-68 can accomodate a BB motor quite nicely. Mine for instance came with a 390 BB, and Shelby's had 427's and 428's.
Also, the FI 5.0 has become a hot mod to do as of late. Apparently it works quite well.
