You dont need to touch the crank, its good for 500hp.

A GT28rs around 20psi plus a few other mods is good for 350bhp.

I know a few FRS' running round with 350bhp on a standard bottom end.

Give GUZZLER a PM he works for Power Engineering, they have done a few conversion on the RS.

Have you concidered just upgrading the compressor housing on the standard GT25? that will be good for aroun 330bhp