According to the Chevrolet Inline Six Cylinder Power Manual, The casting 3850817 is a 230/250 block. Both were the same the difference being the crank and pistons. The crank casting number for a 230 is #3850817 and for a 250 #3962084. The heads are also different and the casting for a 230 is #3824437 and 250 #6259693. These are for Cherolet cars only. The truck section only list block castings. The 230 is for 1966-'70 and the 250 is for 1966-'79. Joe
