Bob, That is interesting that some 21 stud blocks did have insert bearings. When did the 24 studs appear, 1939? My copy of "The V8 Affair" by Ray Miller gives some details on the engine specifications but not all. It seems from what is given that quite a few dimensions on the crank changed in 1939 (59A block) so I am guessing that is the earliest that the Merc crank would fit. Back in the 50s I remember several 59AB engines fitted with the 4" crank and as I recall the '41 Merc had the 3 3/16" bore while the Fords had only the 3 1/16" bore but after WWII both the Fords and Mercs had the same 3 3/16" bore 59AB blocks from '46 to '48. From '49-'52 the Fords again had the smaller 3 3/4" crank while the Mercs had the 4" stroke. A long time ago I had a '38(?) block which I do believe had insert bearings but only 21 studs. I bought it for $10 and planned to put it in a Model A but scrapped it when I realized it was only a 21 stud block and to my youthful mind would not be as good as the 24 stud engines in all the Hot Rod Magazine pictures but that is long ago and the block was later scrapped so that is only a moot point memory. Another useful technical book is "Rebuilding the Famous Ford Flathead" by Ron Bishop which is a paperback that was available from Tab Books, Inc. and it has some better tables of specifications.

Don Shillady
Retired Scientist/teen rodder