Magnum gurus needed

It should be easy enough to get the name of the shop that did the balance/machine work. If you are going to use that timing cover you will need all of the factory Magnum brackets for the alt, a/c, p/s, and use a reverse rotation water pump. Need to check the heads to make sure that the springs don't bind. You have a .506 lift cam with 1.6 ratio rockers. I think the stock valve springs/guides were only good to .500 . You should get a Magnum service manual or one of the Magnum specific engine build books, available on Amazon. If it is internally balance it should have a new balancer/dampner as the original waas externally balanced and would have a weighted balancer. As you know, never assume anything. I would pull caps and check bearings and crank for any potential problems. Bought a reman engine from a Major parts house chain and pulled the main caps and found the crankshaft had a large gouge in the journal. I never trust anything touched by anyone after the factory. I live close if you want to just give up..................
c