A BMW box is most likely but I'm on a Volvo forum and they say Volvo have a rwd box but they are rare from what I can see
Im sure you can use a M90 box from a 940 to rwd a 5 pot motor,im sure they were fitted in 940s from 95 onwards.They can be picked up easy and cheap enough,I paid £100 for mine delivered to the door.There are two types of M90 one is for the redblocks (rwd) and the other is for Whiteblocks (fwd).They are not interchangeable so you will need the rwd version iirc. Here is a handy link with all you need to know
http://forums.turbobricks.com/showthread.php?t=94325
HTH
ps There is a couple of threads on TB of people having converted there whiteblocks to rwd if you want me to post you them ?