Magnum and Wiring Swap

Here's the easy button for a performance tune. Mopar Performance OBD1 PCM for the 5.9. Should work with the 5.2 just fine, maybe with a little extra fuel consumption.

Mopar 90s HIGH PERFORMANCE computer#5249546 - auto parts - by owner - vehicle automotive sale - craigslist

and

Mopar Performance P5249546


Of course, the risk is you have to hope these guys don't scam you, and when the PCM arrives at your door it actually works.