I'll repeat my answer from your other post. Since the AD is a prefix, rather than a suffix, it is an earlier engine--a '41 216 (originally built at the Flint plant) used in the 1/2-ton trucks.

You could verify this by checking the block casting number on the Inliners site.


Curt
----
1953 Chevy 6400, 1957 Chevy 2dr Sedan
--"Mediocrity is easy, the good things take time"