Ive seen an RB26DETT (without the 4wd stuff) in a 4 door R33 and it wasnt as easy as just swapping everything over. It took about three days for a mechanic who specialises in skylines to iron out all the little problems. i think electrics were more of a problem than mechanical. it had bigger turbos, a powerfc and avcr too. that being said, make sure you reasearch it first....