[68WarDog]

Which engine is this? IF it's the original 400, yes it's possible to lift he crank with some difficulty to install the BOP viton seal, the cap size of course is alot easier than the block side. BUT if your engine is now a 455 those anti-rotation holes(block side) will have to be filled to prevent leakage, which means removing the crank, because it's almost impossible to fill them with the crank in place. And as what already been said, tilt engine so that oil completely covers the crank's rear seal and let stand overnight, but you will usually see some leakage in 4/6 hrs if those holes are improperly sealed. Goodluck.