[1976gmc20]

I've actually never had a squarebody pickup with a receiver, but I had two square Suburbans with bolt on receivers so they do fit around the gas tank. Upon reflection it seems that they would fit around the spare tire, but a lot of people move the tire to the bed just to make it easier to access.

In the old days, the fabricated receivers were probably heavily over-engineered. The receiver hitch on the 71 K10 that we had consisted of a welded up and gusseted "goose-neck" of 2" square tube that went up behind the bumper and forward between the frame rails above the spare with a couple heavy angle iron cross members to connect to the frame. If I remember correctly it was built by the Reese dealer and it clearly wasn't meant to come off the pickup again.

The bolt on receivers all or mostly depend on a "torque tube" crossmember under the bumper that connect to arms that reach forward and bolt to the bottom of the frame. Those arms should clear the spare tire depending on how far forward they reach and the diameter of the tire.