Ok, I got some numbers off of both engines.
First, the engine that is IN the truck:
Cyl head: 3836850
Block: Unknown, number not in same place as the spare engine's number
SPARE engine removed from a '55-'57 model truck:
Cyl head: 3836850
Block: 3769925 ('58-'62 261)
The engine that is in the truck has a water pump that extends above the cylinder deck, the spare engine's water pump does not. Are the blocks actually different or are the water pumps just made differently? I suspect the later...
Looks like that cyl head casting number is also for a '58-'62 261. I can't believe I scored TWO 261s.
Last edited by mechanic58; 10/25/2013 8:09 PM.
