Now I see no reason to build a new frame, unless again, what are the expectations? If ones expectations is a show car with mirrors under it, new frame time. But other than that modifying the stock frame which is essentially a pair of 2x5 rectangular "tubing" rails with a few crossmembers. Of course it's 2x5 channel but it works the same, unless of course you are adding a LOT of power and sticky tires. But for your average hot V8 that thick 2x5 channel is plenty.