G'Day guys.
Im Mark. Im in Australia. Im looking at doing an engine conversion in a Nissan Y-61 Patrol. Ive decided on a Cummins, I just need to choose between a 4bt and a 6bt.

Looking at decent numbers out of them. 350bhp from the 4bt and 500bhp from the 6bt.

Modifications are tough over here. Lots of regulations, so its all got to be done properly.

Also need an automatic transmission for it as well. Im leaning towards an Allison 2000 or 3000 6 speed. My knees are shot.

Happy for any input.