I've seen more with uneven numbers than I have with across the board low, 125-130psi was fairly common had a few that actually hit 150 but the average wasn't good.
listen to the way it runs, unless it's been cammed, it should be smooth, let it idle for several minutes. smooth is good.
broken exhaust manifolds, blown out gaskets and broken manifold bolts are common, the repair can be a pain, but can go quickly to, make that a barganing point..
Oh, and check the cooling system, these engines tend to run hot, there should be a cooling fan IN FRONT of the rad that comes on when the AC is on, make sure it works.
Search, Yager has a bit on his (mis)-adventures dialing in his BB Excab little over a year ago.
