The VIN number as assigned by Chevy would be located on a plate on the passenger side cowl at the rear of the engine. If that's gone then yes, an engine block titling is possible. A correct VIN for a 39 1/2 ton would include a number for the plant of manufacture, JC (J being 1939 series and C being a half ton), followed by a number indicating what month in 1938 it was actually manufactured, followed by a number that would indicate what number off the assembly line the truck was. I'm lucky in that Arizona titled mine with a partial VIN that is missing the assembly line number.
If you go to the Inliner's site, the correct 39 head casting would be 838773 and the block would be 838941. I just noticed a new tech tip on the page though that says otherwise. However I was able to accurately date my (2) heads and block using the Inliner's site which has a link under the tech tips.
Does that help? I hope so!
