If I had it to do over again, I would get a nice forged bottom end kit to bring it up to 408ci. Then I would order a set of ported aluminum heads and roller cam from Dwayne Porter. Run EFI on it, and keep the compression below 9.5 so you can add a belt driven centrifugal blower with intercooler.

I used 10 to 1 hyperutectic pistons, a cast crank, wish I would have gone forged with a bit lower compression. I may just change my cam, bolt on the intercooled blower and have it tuned carefully on a dyno. It should last with a good tune if I keep the boost in the single digits.

Magnums are great engines, especially with EFI. The above combination with blower is very streetable and should spin out a reliable 600 hp and lots of torque. That's just about the right amount of hp to keep things interesting.