You can use the rear-end out of any 1/2 or 3/4 ton 73-87 pickup. The half tons will be 10 bolts (some 12 bolts in the earlier years). The 3/4 tons will be 14 bolt FF (and some 14 bolt SF in the later years). You can even use the rear axle out of a 1 ton which will be a 14 bolt FF, but you have to relocate the spring perches.
What I'm trying to say is that there are a lot of options out there. You don't need an axle out of a suburban to put under your suburban. Just match the ratio of the front axle and go!
And, as far as "cheap"...you shouldn't have to pay more than about $200 for any of the axles I listed above (unless the axle has an aftermarket locker or limited slip...then it might be more expensive).