At first I was going "WTF, front drums on a 76 aint right" but I suppose outside the US things may have been different. You could also have a couple of trucks donating their parts to make that one or it could just have been a late build 75 truck that squeaked over to get labeled a 76. Its hard telling with this stuff sometimes. If your 76 truck has the same style of motor (intake and exhaust both on same side) as your 72, then think of it as a 75 when reading any of our egocentric USA based info.

That should help you keep from thinking we're all crazy.
Front discs are a really good upgrade, and not too hard to do if you can find the parts. I think if you can find the caliper bracket and a hose you could buy new/rebuilt parts for almost everything else. Maybe someone should update the how-to in the info section of luvtruck.com with a shopping list of part numbers needed to buy it new.