Not sure if there's any play back and forth, I don't think so though, because the mechanic has inspected the shaft and seems to think it's fine. I think you're definately right, I'll have to take the box out and make sure it's all ok. Thanks for the advice mate. And I suppose while I'm at it I should really look at putting the SP box from the old engine into this one (it's not doing much good sitting on my bedroom floor).

Will the SP gearbox/clutch drop straight into that R case? Or are there modifications I will need to make? How did u go doing yours?