Modifying a steering box

[waco]

I am working on a '78 Chevy P10 with manual steering & would like to convert it to P/S. I have a '79 4x4 with a P/S box on it for parts. I know that the '79 4x4 will not work as a bolt in, but if I can change the sector shaft from the 2wd box into the '79 4wd box it will then have the correct shaft end for the 2wd pitman arm. I have read on another site that it is a doable swap, but would like to confirm this as a parts swap without any machining of parts. No instructions were given. If this swap will work it would also make for a cheap P/S swap on 4x4 adding crossover steering to a 4x4, maybe.

All input is appreciated.

Thanks

Andy