Yes, the guy who was looking at the blocks is a reputed builder of older engines, and quite possibly this was the process he would use.
(I guess I just call all metal repair "welding")
Original block cracked between exhaust valves and water jacket, and much corrosion.
Second block between #3 and #4 cylinders, first he thought this one was possible, but further inspection said no.
I totally trust his diagnosis, as he is into keeping oldies on the road.
Seems early 6 cyl. blocks here are less common than 4's, and the Standard 6 only ran 2 yrs production, 13 yrs or so for 4's.
I have e few 4 cyl. blocks, spares for the '24 , it still runs orig. block, rebuilt. (Been in the family since 1932.)
In no rush to swap out original gear, still have a few avenues to hopefully find an orig. engine/block.
The 251 had been in boat, so needs a lot done for car use, was just looking at options.
cheers