The 3-7-68 is the build date.
The "maltese cross" means the bearings are .001 undersize.
The NM42624290001 should be the casting # with sequence, but the number doesn't look like anything I have seen.

The stampings on the pad are weird too.
They should be F(letter) 426, with the letter being the year, with 1968 = D, but I have never seen SM 105.

So check that you have cross bolts on the center 3 mains, and that the top 4 head studs go into the valley area. That's the real way to tell if it's a Hemi block.

If it is a Hemi block, then I suspect it was purchased separately and was not part of a production build.