I have a question on identifying year of v8 flathead. I have 24 stud offenhouser heads. The block number on top rear near intake is K21. The cast number at rear of engine on stubby bell housing is F1913. The bell housing that mounts the tranny is bolted on to engine. The water outlets are forward on the heads and the distributor is modern MSN. The bolt pattern on the flywheel for the pressure plate is even spaces all around and is 10". Can I get a little help here. I can't find where all these items fit into a single group of years. Bob