Differences Between Gearboxes Rb20,25,30

[Scudsicins27]

Hi everyone I just got an r32 it shattered a pressure plate and made a bit of a mess to the gearbox it is supposedly a rb30 box and I got given a box with it that is meant to be an rb20 box the suposed 20 box has a longer extension housing and less webbing in the case, I had a quick look on eBay for a 20 box and found a reco one that was the same length and case as my 30 box, I am new to the import side of things and don't know a lot about them. But I was wondering if anyone could tell me the differences between the boxes wether I can swap bell housings or extension housings and different strengths between them all and what bolt up behind what?

[GTSBoy]

There is the big box and the small box. The big box is the basis of the RB30ET, VG30DET(T) gearbox and the RB25DET gearbox (and related to the RB26DET box). The small box is the RB30E, RB20DET, RB25DE one, and there are various flavours amongst those.

You cannot swap anything between the big and small, but you can generally swap front half and hack halves between variants of the big (and variants of the small).