Yeah, as MTBER said... the stroke is slightly longer on the B18B then the C motors.

B18B rods - 3.504" , R/S: 1.571
B18C rods - 3.433", R/S 1.581

Very minimal difference.

The GSR rods/piston combo will be able to revslightly more and make hp higher in the rpm band. However the LS rods/piston combo will make slightly more tq and will be able to rev slightly lower.