390 REAR MAIN LEAK..HELP!

I have a 67 390 that we have redone and put into my dads 73 F350 camper special. The engine came out of an old bird I used to own and when we tore it down we found it was not just the run of the mill 390. It looked to be similar to the old PI 390. Anyway, after 30 over, crank turned, flattops, a cam and carb, we have an oil leak that will not go away. The rear main is leaking after trying a lip seal type seal and a rope style seal. A friend of my brothers told him the block is worn out at the rear main. My father was a master mechanic at a ford dealer for 30 years and he just is not buying that the block is worn out. I am having somewhat of a hard time with that idea as well. I do know that the engine has not been hurt, and was not leaking a drop when it was in the bird. Anyone have an idea about this? I need a new perspective on what might be wrong here. Thanks everyone!
Randy
Hartland, Mi

groove worn in crank maybe?

No groove in the crank...all of the cross cuts in that main are all still in very good condition too..they are not worn off.

Did you stagger the seals halfs so they don't meet on the rear main register?


[addsig]

We recently had a similar problem with a 427.
Make sure:
-the pins that hold the rope seal in are out if you use a modern seal.
-the three block plugs on the back of the block are in and tight.
-the PCV system is operational.
-the seal is in the right way.
-stagger the ends in the main cap.
-silicone the crap out of it and the side seals.
-the oil pan isn't the real problem
Mike