Yes you can fit an rb30 into a z31 things you will need are ( 200zr X-member, series 1 rx7 engine mounts and a modified front sump which will need to be made to clear the power steering lines and will need to get new power steering lines made due to power steering pump is on the other side of the motor will need to make radiator mounts due to the rb30 the original radiator won't fit also will need to run electric thermo fans too and also will need to make up a new radiator top line to have the filler neck high due to on the vg30et the filler neck is on the radiator and also on the rb30s it's on the radiator for the gearbox will need to make a gearbox mount and get a custom 1 piece tail shaft made too ) there is more like wiring but that's the easy part that's what I have done to make an rb30 fit into a z31
