if its a half ton, it has 10 bolts front and rear in 86, that is, saying the running gear is stock, it should be a 700r4 and a 208 as well
you can swap in a 14bolt full floater and a 10 bolt from a 3/4 ton if you want a heavier rear axle, if you want heavier front and rears you would want to go one ton
14 bolt full floaters can be had in 3/4 OR 1 ton trucks, the only difference between a 3/4 and one ton 14bff is the shock mounts, 3/4 ton will have them on opposite sides and 1 ton will be shocks mounted on the same side...
14bsf did not show up until later years.... you inherited which i assume means you got it for free, so you have a great base for a build because you wont feel bad about hacking on your well spent money...