(quoted from post at 17:35:15 09/26/16) I guess the root of my comment was that I am partial to the Char Lynn units. I have two here on the farm, and some JD units as well. The Char Lynn units require no adjustment, and are a lot simpler. I used to cultivate 200 acres or so with an A, a 4 row front mount cultivator, and a Charlynn power steeering. And even with the rigs on, after a long hot day, she'd still steer with one finger. It was, and still is, a one finger unit. Installed in the very early 70's, it still will steer like a 4020.
My experience with the JD units is this: Yes, you can make them steer well. But it takes A LOT of patience, and it may or may not work perfectly in the end. I had an uncle (now deceased) that loved to play with 'em. And he could get them to work well. If well adjusted, he be proud if he could dig a hole in the driveway by spinning the wheels back and forth with one finger. Even he would admit though, that his 70 gas with char lynn would steer better- and that was with a mounted picker! The worst deal with the Deere units is finding the happy medium of performance between hot oil and cold oil. Oftentimes, the Deere unit would steer great cold, but would lose their ability when the oil got hot after a few hours. Or the opposite- great when hot, but would flutter badly when the oil was cold.
And so my opinion is it would be a lot simpler to find a Char Lynn pump for the front end than it would be to swap out a front pedistal, fan shaft etc, and then rebuild to factory specs... keeping in mind that the Deere original 70 power steering was frequently updated to the newer style actuating sleeve etc of a later 720/730. I think it would be shorter upfront cash outlay, and longer term reliability. Beiung the tractor is already equipped, why not just find the correct pump?