They didn't put 14 bolts in these trucks, '73 was the first year if i remember right. Stock rear would have been a Dana 60 (odd shaped cover, 10 bolts) or a HO52 (round cover, also 10 bolts i think). The 14 bolt rear, which could have been swapped in has 14 bolts on the cover. The semifloating rear has a more oval shaped rear cover, while the full floater has an odd shaped cover, kinda like the Dana 60 rear. Also, the full floater will have exposed hubs at the end with a circle of bolts on them, portruding from the wheel stud area, beyond the wheel studs.
For a axle ID guide, go here:
http://www.offroaders.com/info/tech-.../axlefacts.htm