Keep in mind that a diesel like the 6.2L or 6.5L usually has a sweet spot around 1800 RPM, much lower than the stock truck engine would have.
For best results, gearing changes will be needed.
I am thinking about eventually putting a diesel in my 1967 C50, but it would be a long ways down the road...
To deal with the gearing issue I am planning on installing an divorced NP205 transfer case backwards to act as an .5 overdrive. This along with my SM420 and two speed rear end should give me plenty of gearing options for either a gas or diesel engine, and handle cruising at 55-60mph.
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