Steering box conversion

[71/454]

I have a 71 1/2 ton(soon to be a swb) with power steering, but the box is leaking down by the rag joint. Talked to a friend today who is in the transmission/steering business to see if he could just put a new seal in it. But he says the box is more than likely worn out and changing the seal won't help. A new box is over three hundred bucks. My question is this can I just swap in a box out of a 73-87 1/2 ton thats clean and not leaking? These can be had for a much more reasonable price of free or some beer. I already have the newer steering linkage anyway because I changed the spindles. Thanks