3 point

Yes the two valve bodies are all that need to be changed. The bolts are different lengths and the top right bolt (facing the rear of the tractor) has to have a copper washer under the head instead of a lock washer oil will leak out. If you obtain a valve body off of a numbered series tractor (50, 60 etc) they had higher break pressures for the relief valves than the lettered tractors. There are differences in the check valves of the various (A, B, G, 50, 60, 70) Power-Trol units but these primarily affect the slow riase/drop feature. If you put a G power trol valve on the B & connect it to a small bore remote cylinder, the slow raise/drop features will be affected. Since you're going to use just the rockshaft I doubt you'd notice any differences.