My pal Kenny did a gas to diesel conversion.
Bought a complete diesel from a power unit to put in a 63 2000 industrial
It wasn't as straightforward as one might think.
Throttle linkage, air filter, tank mount brackets, fuel tank, battery tray, 12V vs 6V electrical system, to name a few - all had to be changed or modified.
If you are serious about doing the switch Larry D in Lousianna had most of the parts we needed to make the change. Good man to deal with.