I found a reman by Cardone for a little over $200 including the core and shipping. I think I'm going that route.
you can do the rebuild yourself once everything is nice and clean it comes apart and goes back together fairly easy http://www.autozone.com/autozone/parts/_/N-8koj4?checkfit=true&itemIdentifier=21507_0_0_
Have you tried adjusting the control valve to see if that is the problem? http://1bad6t.com/Maverick/repair/steering_02.html
I thought there was a conversion kit available that simply eliminates the power cylinder & control valve (?).
I used one of those and it was...crap...very sloppy steering... not saying they don't have a better one now...
I have one of the newer better ones on my borgeson setup right now, it came with the power steering gearbox conversion. It does ok but honestly im going to replace it with a manual centerlink and pitman arm as soon as possible. To buy the conversion joints you are still looking in the $150 range. http://www.summitracing.com/parts/brg-990003/overview/make/ford