Specifically, can these engines withstand reasonably high loads for extend periods of time ( Not high RPM ) without overheating ?

I have a nice 77 Chevy pickup that needs an engine and replacing the 350 is too easy. I've collected enough parts to install a 4BT Cummins but am now resisting due to noise. A 6.0 LS motor was a possibility but is too easy / boring.

The next step is a late Jaguar V12 simply because it will be an interesting swap with " what just went by? " exhaust note. My 80 Chevy 1 ton has a 292 in line 6 with good sound so I want to keep with that same format.

I'm resisting a Mercedes V12 mostly because I'm already doing the inline 6 Mercedes thing. Also the Jag uses a GM transmission so drive shaft flanges / shifter are a bolt on swap.