Originally Posted by R_W
Do you still have a working gearbox on top?
Do you know the stroke? Most of them were LONG
You can use two check valves and an airspring with enough travel and PSI(or a lever rig to convert travel to more power). $100 if you buy it new.
EDIT TO ADD: It would be best to set up two in a push-pull setup to take advantage of both sides of the stroke.
It's a fairly short stroke, 6-8". My 1st thought was to use one of our old pump jacks that we used when the wind died. They have two large pullies that hook to the drive-shaft on a Briggs & Scrapiron 5hp motor. Maybe put the compressor where the gas engine used to go?
I'll have to get some pictures.