I tested one of those '72 HD 413's and still have the data. What I can remember is that it seemed thicker but NOT to the point that it would be as thick as a normal 440 block when bored to 440 size. I still have one of those blocks at standard bore if anyone in NW Oregon or SW Washington is in need.
Needing to use a smaller bore you might want to really consider intake valve shrouding. It might be better off with a 2.14" valve than a 2.19" or bigger.
Chrysler never cast any block for cold weather. That's a silly notion spread on the internet.
I've read rumors both ways on 413 cold weather that they a 440 under bored to they a normal block, really know I need to sonic check to be sure but figured maybe someone could give alittle insight befor hand, block he no casting numbers on sides and in bell I think it was 8R...
