For starters, have you looked at the 125 DC's in the Tractor Photos at the left? They are sure to provide some guidance.
1948 would be the last year of the "motor lift" mounted implement hitch. In 1949 hydraulics first became available. 1952 marked the first Eagle Hitch, Case's version of three point hitch.
I understand people have modified the pre-eagle hitch lifting systems to fit three point implements, but I've never seen such a conversion in the flesh. Your system works very nicely on the mounted Case cultivators designed for pre-eagle hitch equipped tractors.
Hopefully someone with conversion experience will post.