Silverfox,
Why a 18RG? Why not a 2TG. The 18RG will not bolt straight in.. Unless you can get a crossmember from a RA21 from the states, then your going to have to change your mounts. It will fit, but not as easy as a 2TG which will bolt straight in, no problems.
You will have to use a W50 or so, as a T50 won't bolt up to the motor.