Friend bought a 42 ford truck that was partially torn down for paint years ago. While torn down that owner bought a couple more flatheads. They are all residing in the box now. There was nothing wrong with the original when removed. So how does he determine which is the stocker? The old owner that did the teardown is no longer around to help with ID.
If it was the factory block that came with the truck and had not been replaced at some point. No 59 cast into it. Two fan belt system. 2 hole dizzy. 81A also had a slight raised intake deck. http://www.vanpeltsales.com/FH_web/flathead_specs-85to100mid.htm
1942 was not 59, those were post war. The "raised deck" blocks are 1941-1942 only, so if he has one, that is the stocker. For all your 65 / 75 / 85 / 90 / 100 / 110 / 125 horsepower flathead Ford V8 engine block identification needs:http://goldengatev8.org/tips/EvolutionOfTheFlathead.pdf
A PS on that...all the '42's as far as I know (the engines were used throughout WWII as well, produced in US, Canadian, and German factories!) had that raise pad (actually, same old level with lowered shoulders, if you want to be correct), but both 221's and 239's were available in trucks. Look at the CENTER keystone shaped water passage in th pic above: that engine is a 221. That center hole was round in 239's.
Well it turns out they're all 8BAs, so none are stock, we did figure which one most likely came out of the truck. There is also a spare transmission that must be earlier set up for a closed driveshaft. And the one that should be from the truck as the 42s are first year open and of all things extra a flat 6 radiator. Both flatheads (only 2 not 3} are non-bellhousing versions, and even the spare is pretty complete.
If you want to build a substitute original, any raised deck '42 or wartime engine will do it...serial is on the trans case, so any appropriately chosen engine will be indistiguishable from original. 221 (18 serial number on original trans) and 239 (99 serial on trans) were both available and are actually indistinguishable once fully assembled.
If the engine was never in a machine shop....check on the intake surface, driver side, toward the rear of the block. If it was ever "decked"...numbers will be gone. 8BA = No bellhousing. 4TTRUK