I presently have both the new valve, and the old soldered in valve which I unsoldered, in front of me. Here's some dimension differences:
Outside diameters - old valve .769
new valve .771
Old valve has a flat inlet end, and the new one has the typical tapered end which may make the original piston a tad bit too long. A problem to consider.
The body length is the same ( not counting the tapered end on the new one )
The pressure outlet hole on the new one is prox .040 closer to the back end.
This outlet hole must line up with the barrel hole so if you position the whole valve .040" farther forward to line up the transfer holes you would bring the front of the valve even farther forward and then quite likely would have to shorten the piston rod.
Be careful in sanding out the solder after the old valve has been removed. You only have .002 " of pump tube ID to work with.
I agree that it could be done, but with a " whole boat load of work ".