Thanks guys.
I just managed to download the Tremec TR-3550/TKO service manual. It calls for 3 quarts.
Man, gotta wonder where this guy got 21 quarts from? Makes me doubt the rest of his notes somewhat, too.
So, does 7 quarts of 10W40
oil sound about right for a 351W/392 with functional
oil cooler? It seems about right to me, but then I'm just a new owner.