[D13]

6.2 has nothing to do with Olds engines. You should be able to drop any 73-86 truck SBC into it. You will need to change the converter, your best bet is actulally to swap the trans as the shift points will be at lower RPM. Diesel truck will have a low axle ratio which you will want to swap for a hot rod. You will need a gasser wiring harness. You can flush the tank or swap it.
Quite frankly unlless this is the exact body, color, and trim level you want, or dirt cheap, you'd be better off looking for a gasser, as at the end of the day, the easiest way to convert is to buy a gasser and swap eveything over. Now you've got 2x truck and a lot of time invested.
Cummns conversion is great but way more money.