Novarossi won't fit, the crankpin is different (if I can remember right it is larger), maybe the rods of a RB will work. The piston pins are different so when building up you do need the rod beloning to the P/S set. I did fit a GRP set into a Novarossi engine and with using a NR rod I only needed to drill up the hole from the piston pin from 4mm up to 4.2mm
I know the early REDS racing models were based on GRP messurements or you have to look at the new Techonpower engines which actually are the GRP engines. Only no onroad P/S set but probbebly you only need to raise the exhaust port.
On the other hand, the time and costs is not worth it, getting a new engine seems to me like a better choice.
Speed is only fiction but a 130+km/h MRS4 is for real.