5.9 and 360 LA use same parts?

Pulling an engine out of a Durango sucks. Been there, done that. I'd let them handle it.

The Magnum uses a unique balance. It is not the same as LA 360. All 5.9 magnums are the same, though. Any 5.9 magnum flexplate should work on any 5.9 magnum. 5.2 magnums are internally balanced so balancers and flexplates off of the 5.2 will not work with the 5.9.

To have proper balance you want the oem flexplate and correct harmonic balancer/dampener. That's the easiest way to do it. Sometimes the Magnum will have a serpentine pulley integrated into the balancer, if this is the case and you want to use a V-belt pulley system, you need to source a balancer without the attached pulley.

I do not know if the durango manifolds will fit the early a-body or not. It sure didn't seem like they would work for my '71.

There's a lot of information at the link in my sig.

Good luck.