Low Oil pressure

Did you check to see if all of the oil galley plugs were installed when assembling the block?

I had a similar problem on the first engine that I rebuilt. I finally found the problem to be the machine shop didn't install the oil galley plugs that go behind the camshaft thrust plate.

Look in this post below to see where they are:

http://www.forabodiesonly.com/mopar/showthread.php?t=287231