Step 0 for both of you. Grab your year's factory service manual.
RC96SLT - one thing that helps is that the 1996 was OBDII, so even though a 5.9 was not a factory option, you can pick up a V8 ECU, a 5.9 and a 46RE, add the two injector wires from the engine harness connector to the ECU, and go. Past that, call a tuner to get the max out of that 5.9. The 5.9 will need a Dakota oil pan, so ideally you find a Dakota donor for it; but if not, the pan can be bought.
And as mentioned, it can be stroked and bored slightly to 408ci/6.7L.
RwP