[Excaliber]

SPF and FFR (I THINK FFR) use the Ford 8.8 IRS typically found in T-Birds and some Lincolns. Not sure how that compares to the Mustang IRS components. That said, a live axle properly setup is MUCH cheaper and depending on track conditions will perform close to or as good as an IRS.

All though re-sale should not be a huge issue you can really hurt the future value with certain largely undesireable "options". Auto trans, non Ford engine, to much "custom" interior, exterior, etc.

It would be advisable to stay within standard accepted practices when building your replica. Stirpes should be as per known "specs", for instance.

FFR and JBL are worlds apart in "cost". A really well setup FFR MIGHT be able to hang with a JBL, but I wouldn't bet on it! I would not consider either of those body styles as "accurate" as other choices. But you were talking about "handling" not "looks".