I've been running a mildly warmed over 5.9 in front of the original NV2500 in my '88 Dak for a few years now, no issues. I've kept an AX15 in reserve as a backup, but so far it hasn't been necessary.
The 5.9 bolted right in using the V6 mounts (and a Durango oil pan), just had to rebalance the flywheel. With a 5.2 you wouldn't even have to rebalance, since the V6 and 5.2 are both neutral balance.