This is all very interesting. Glad I posted. Didn't realize my block was walking a line. The casting date stamp is L 285 so December 28, 1955. The stamp next to the distributor isn't really clear in the picture, I'll have a look after work. I've always had trouble matching this stamp to info available online due to being in Canada. I'll also post the casting number after work, as it's hidden in the picture, but that's more for interests sake. Pretty sure I've looked up the casting number in the past, and don't remember it pointing to a '56, but that was a while ago. . .
Jerry and others, thanks for the tip on physically checking the bearing. I'll pop a bearing cap off after work. Just for clarity, I assume the positioning tab I'm looking for is the one I've circled in the attached picture?
After reading the info presented in this thread, I'm finding searching for bearings quite frustrating. When I mistakenly searched for bearings for a '54, the 460M part number repeatedly came up. I was under the impression that the difference between the 460M and the 853M was that the 960M was grooved for half the bearing and the 853M was grooved for the full bearing. One website seemed gave a choice between a 960M and an 853M for the '54. At the same time, this is immensely entertaining. Putting problems/puzzles to bed is fun.
As for the bearings being under/oversized, guess that's just a vernacular issue on my part. .01 was taken off my crank. I assumed the extra material on the bearing would result in calling it oversized. I'll adjust to the vocabulary of the pros.
Last thing, bearing cap shims. I honestly don't remember if the shims were there. I am aware of them as the original engine for my truck was a 216 that I stripped a couple times. However, when I mocked the engine up to measure for valve to piston contact and I snugged the main bearing caps, with the original non-undersized bearings, I couldn't turn the crank with the bearing caps not even fully torqued yet and had to back off the bearing bolts. From that, I'm assuming I'll need the shims, and thinking they were there and I tossed them anticipating buying new ones.
On a side note, my machinist told me I could get away with using the original non-undersized bearings if I needed too. I'd rather get the proper sized bearings though.
