should be. I mean, if you had a R32 GTS4 wreck and no one wanted to buy the engine, you'd sell it cheaper so someone took it right? Cars that AWD RB20DE's feature in, in general are rustheaps (as most of them were used in snowy areas in japan... hence the need for AWD) so its not like there's any shortage of spare engines.
And if you can't find an RB20DET, then put an RB26DETT in, or an RB25DET out of a stagea (which is pretty tricky, but doable).