Unimog Club UK

Hi Kev, and welcome
A Bt6, you may have to bolt the tyres to the wheels to stop them turning
Have a look around on the internet, people have put all sorts of engines into unimogs with varying degrees of success.
A Bt4 may be a lot easier or if it converted to Perkins how about a 1004 Phaser turbo, they are a good motor with a manual pump and excellent spares availability?
whatever you go for I'm sure everyone one here will be pleased to hear how you get on.

Cheers
Tony