Hi chaps, I've got a 360 at the moment, put a welded diff in it yesterday and seem to have lunched my gearbox . It still drives but theres lots of grinding and scraping and it's difficult to select gears. Fourth is fine though oddly. I'm going to flush the diff and box out tomorrow and see what comes out. I've found a 340 box and diff already down in Dorset but I've no idea if these are compatible. My gearbox was on it's way out before I put the welder in it but I wanted to spend some time getting a decent one sorted. My hand, however, has been forced.
I believe the gearboxes are mostly the same, provided they have the same number of gears. The front input section can be swapped over, but I have not done this myself, others have posted about it.