What sort of RPM could I expect from a typical MVVS 40 using 0% or 5 % nitro, the 3248 mini pipe and an APC 10x6 prop? I have an upcoming project that I think the MVVS 40 would be suitable for, but I am not sure what power I could expect from it.

expect about 13,000 rpm. A well tuned header length maybe a bit more.

Hi!
If you change the rear ball bearing to a WIB C4 bearing, removed the head shim, Used a Nova Rossi 4 or 4A glow plug, you could expect around 14000-15000 rpm using the MVVS 3248 mini pipe.

The standard MVVS .40 engine turns a 10x6 APC at around 13200-13600 rpm on FAI (80/20) fuel.
Best 10x6 prop is either a RAM or Graupner "Cam-prop", not an APC!

My suggestions are always a bit pessimistic. Better to err low than to create disappointments.