Re: New block
In the 21 stud range there were the 32 thru part of 35 that were all very similar with only minor machining & casting changes. Then the late 35/36 with replaceable bearing shells and the 37/38 block with the first block mounted pumps.
24 stud blocks started with the 38 through 40 221 CID with the 239 CID blocks starting in 1939. The 1939 99A block was supposed to be the one that had the thickest cylinder walls for boring of all the flathead blocks. In 1941, the castings changed in several ways but I'm not sure how far it went internally. They did away with the core sand holes in the pan rails and reduced the amount of iron around the intake deck. This was also done to the 239 CID blocks and these carried through to WWII. It's possible that the 19A (1941) 239 blocks had the same cylinder wall thickness as the post war blocks but I don't know that for sure.
The post war 59 series was a good solid 239 block but there was also the 41A type that was a replacement for prewar 221 blocks but had some characteristics of the 59A block as well. I'm sure they used some of the same cores between the two but not all since the 221 had thinner cylinder walls.
8BA blocks had three changes but they were mostly machining changes to valve pockets without hard seats and such. The basic block stayed the same all the way through the end of production.
I'd love it if you could get any block you wanted but obviously a person would have to draw a line there somewhere with that many changes during the flathead era. Where to draw it is up to the person doing the production on the project. I'd settle for 8BA myself but others might like the 59 type block. Make a 59 type casting that could be set up for machine capability for either 21 stud or 24 would give more choices for those folks and keep production casting to a minimum. Something else to think about anyway.
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