Technical Mopar flathead six ID

I just bought a 50 Dodge Coronet Club Coupe, in pieces, with a parts car. The fun begins. I plan to go with a small block Mopar and lower it, after, of course, the requisite rust repair, etc.
The flathead that came with it has a number stamped on the block of IND5A257570. It's on the left side, between cyl 1 & 2, right where the number is supposed to be. I can't find ID for that. Can anyone help?

 

Yup, an Industrial Mopar 6, a lot more heavy duty than the 218 or 230 that would have been stock.
You have a 23 inch 218 industrial in there.
http://www.t137.com/registry/help/otherengines/indengines.php

 

Oh yah go here for a lot more info and help with this car and drivetrain.
http://p15-d24.com/

 

Thanks for your help.

 

IND5A is an industrial engine, 218 cu in. Measure the length of the head to find if it is a Plym/Dodge block (23 1/4) or a DeSoto/Chrysler block (25" long).

See if there is a metal tag rivetted to the right side of the block, along the pan rail, in the middle of the block.