1 ton 4X4's are a little more common around here in the snow belt...
I remember seeing 73-87 1 ton dually 4X4's quite often when they were on the road... not so much any more.
the suspension switch should be pretty straight forward when you find one, I assume drilling and removing all the 1 ton stuff, and just bolting it on your frame. similar with what I did on my suburban build.
here are a couple in mt
http://greatfalls.craigslist.org/pts/5038543279.html
http://kalispell.craigslist.org/cto/5114597677.html
2 in your area, but expensive:
http://phoenix.craigslist.org/evl/cto/5100014315.html
http://phoenix.craigslist.org/nph/pts/5111947586.html