Are you sure that first number is an 8.
There is a block casting 3788406. It's for a 1963-64 230. Used in car and truck.
1965 thru 1970 had 3 block casting #'s for a 230 truck, 3850817, 3854036, 3877178. These same block casting #'s were also used from 1967-72 for a 250.
A 292 from 1963-66, casting 3789404, 3851659, 3921970, and had 7/16" bolt holes in the crankshaft flange.
