[LMH]

Backdraft is a little longer wheelbase I think. Rear fender has a more bulbous shape to it than original 427's. Well made car from what I've seen.
SPF and FFR are both 90" wheelbase. I'd also say SPF is the most original in shape of those three. SPF's are factory made and good quality control over the product.
FFR's are as good as the builder. Shape is more of a 'inspired' body though I haven't seen a MKIV in person yet.
To answer your question, there are differences in each shape you've asked about. There are differences in pretty much a of them when compared to originals.
Then there are differences in one original to the next too. Slight but differences.

So are you really confussed now?!!
Larry