I grew up on Land Rovers. My dad's LWB 2.6 6-cylinder 'Safari' was so much fun... And in the wet, broadside around roundabouts was a must.
We fitted all sorts of engines to them. Aside from the Rover (ex-Buick) V8, we used a GM 6.5 turbo-diesel V8s, 318ci Chrysler engines, V6 Ford Cologne... I stuck with my 2.25 '4', but with some work got 175bhp out of even that.
It's all academic though. There's only so much power you can actually use in a leaf-sprung ladder-chassis truck. The rest is fun, but ultimately pointless.