Drop me a private message and I'll be glad to share the method of fitting and checking oil clearance on Babbit rods that I learned back in the 1950's. It's a little complicated, but that type of bearing can be clearance-adjusted repeatedly, as long as there's some soft metal left in the big end of the rod. I believe I've still got some reconditioned 207 rods stashed away that I'll probably never use, that might be useful to you.
Running the engine with the damper off will guarantee a leak. The damper hub should have a reverse spiral that pushes the oil back toward the slinger, and there should also be some weep holes for the oil to run through back into the crankcase. All those passages and the helix on the damper hub can get clogged with sludge. Loose main bearing clearances can also cause oil leaks from the crankshaft bouncing up and down.
Jerry
