5.9 Magnum block with a 4" crank and then the AAR top end put on it. Install a decent roller cam and it would be a fun little engine. Only visual drawback is no mechanical fuel pump on the 5.9 block if your trying to keep it close to original looking. If that is the case then an LA block would be better suited. Forged pistons and better rods + ARP bolts would help ensure it stays together as piston speed increases with the longer stroke.

4" crank would boost the low and mid range torque up and get the car moving easier, which is ideal on the street.

You could still run the exhaust manifolds, but it would be good to make the rest of the exhaust as free flowing as possible.