Thanks Charlie in MO and Haas. I'm still thinking.
It appears that this engine has Zollner pistons. The sleeve bore is 3.1875. Pistons are stamped with Z and 4079 as well as with IH Part Number 374294 R1 CAM-Z16.
I have nothing but time on my hands and was wanting to get this old engine running pretty much "as is" then decide where to go from there.
However, I busted one of the sleeves in removing a piston. Don't remember how, but I did.