Since you are looking at a vehicle which only had one rear axle, any axle you find will require brake line, parking brake, ds yoke, leaf perches, r&p (other ratios/lockers availability) and shock mounts all to be looked at or weighed when you decide to buy.
For the most easiest bolt in would be to locate someone else's sale for their next upgrade.
In terms of cost, labor and time, like what FourbangerYJ suggested. However, costs also depend on demand and your location. Other viable rear axles are available with minimal work effort.
Good luck.