knuck pistons

[Colonel-46-El]

please,anybody what's difference between "36-40''41-47"(61)OEM pistons thank you the Colonel.

[kitabel]

AFAIK the ring lands & grooves and the ring set. The later is preferred, but I'm not sure w/r/t the "female rod in front" etc. oil control thing. If you have a '46 you should be using the later pistons.
IIRC the 1936-39 EL uses the same ring set (but not pistons) as the 1937-? U/UL, same bore size.