Sorry Ra23, As RA40Celica pointed out, there are differances.I have also heard that the 18R block is NOT AS STRONG (sidewalls/waterackets)as the 18RG block. And as Norbie stated , It would be much easier and hassle free just to source an 18RG. In my opinion, you would be better off just getting the 18RG package, And even if its fucked and needs a rebuild, You will still be better off in the long run, having a nice reco 18RG to cruise the streets with.