Hiya,I put a TDI engine in mine .I used the VM gearbox with a TDI bell housing which was a direct swap.The only thing i had trouble with was the spigot bush in the end of the crankshaft.The outside diameter is the same but internal diameter is smaller for the VM gearbox output shaft.I got a bush made by a local engineering firm and all was well.
hope this helps.
Paul