I dont have a FRC, but a z06, but would like to get in on this:
here's what I think in camparisons
-97-04 vette= 87-93 5.0:they are both the most loved mustangs and vettes so far!)
-99-00 FRC= 5.0 notchbacks: they were both the lighest of their original models and Non-hatchbacks and mostly rare and faster
(I put the z06 aside with the cobras just to make sense of these comparisons

)
So my opinion if I already had a FRC, I would keep, play with it, not mod the hell of it but Mod it enough to make it interesting, and I would start having something unique and rare. Just think of those who sold their rare Notchback 5.0s, and now they regret it and I believe those notchback sell for more then the Hatchbacks, just for its Rarety