I'd run 10w-30 oil with MMO or trans fluid in it for a little while, flush it out and refill it with 20w-50. Or use HRL's overfilled deisel/oil mix for 20 minutes, drain and fill with 20w-50.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)