Check to be sure the road draft tube isn't clogged up. Unless there's a good vent system, crankcase pressure can push oil past even a good seal. Unless some detailed cleaning was done during the rebuild, chances are that the road tube isn't doing its job properly. It only works at speeds above 30 MPH anyway, so unless you put some miles on the truck above local street speed, the crankcase doesn't get vented well. The timing cover seal can be changed from the front side- - - -no need to pull the oil pan or the timing cover just to install a seal. Put a "Speedy Sleeve" on the balancer hub while it's removed. The same one that fits a small block V8 works on Stovebolt balancers. That expands the sealing surface by a few thousandths and makes the seal work better.
Jerry
