1992 Mazda Truck front crank seal failure

I have a Mazda B2600i, pickup, 4wd, auto, 180K miles. I had the engine rebuilt, (cam, rings, pistons, crank, berings, head, valves, oil pump etc). Now oil pressure (hot/idle) is 12-14 psi (seems low!), But at startup can go up to 80 psi (seems high). It ran ok for about 6 mos, then it pushed out the front main oil seal, (lip type). They replaced it and this has happened two more times (with new seal). All parts check out and seem to fit correctly. They have no idea why the seal will not stay in. The oil pump is driven by the crank very near the inside area of the lip seal. I am wondering if for some reason the seal is seeing full oil pressure and if there is supposed to be a vent between the seal and the pump that keeps the seal from seeing full pressure and if it was assembled incorrectly, full pressure is pushing the seal out?

Any clue would help. Thank you very much.