Welcome, Fernando!!
With a FFR under your belt, you'll be right at home with the process of building a 40, although you'll face some engineering challenges with the mid-engine layout you didn't have with the roadster.
Get yourself a Daytona after you build you GT40 and you'll be able to die a happy man, with the holy trinity of replicars!!
As for the RCR compared to the other kits, well...........................................................................(here we go again).
Doug