Well i've narrowed it down to either:
* Perkins 4236 + 5 speed box
* Perkins 6247 + 5 speed box
Both engines were fitted to dodge 50's so are cheap and readily available. I've heard that the 6247 has less torque than the 4236 and has a non-to-reliable pump as well as hard to find parts? So perhaps better off with the slighty less smooth but more relable 4 cylinder (Phazor) 4236 engine.
Any further thoughts folks???