you could use it, but you will need to custom fab the ebrake lines, swap axle shafts to the 4x4 ones of the 86+ axles (they are wider than pre 86) the third member is an 8" is a v6 third and probably has really high gearing... if its got a v6 and its 2wd it is most liekly a 1 ton truck, or some wierd combo of parts frankentruck.... also will need to perfrom a SOA to it as the 2wd axles were spring under.....
for the amount of work involved, i would jsut find a 4x4 rear end from a 86+
