[BILT4ME]

Most likely stock tire size is a 7.50-16 bias ply mud/snow tire. Generally, they were about 31" OAH.

"Stock Height" is a relative term, and it depends on where the measurement is taken.

Someone here has frame dimensions and I believe there are dimensions from the frame in given areas to the ground.

Some folks try to measure from the center of a hub to the bottom of a fender lip. That will identify any "lift", but I'm not sure that it was ever a "stock" dimension that was documented.

You may be able to find an overall height dimension to the top of the cab, but that could be influenced by tire diameter and what YOUR truck was equipped with.

The 68 K20 we had lots of years ago came with 7.50-16 mud tires, but we changed tires many times during the life of that truck, so the overall height would have varied. It was also the HD version and the "stock' dimesnions are usually given from the base model truck and that MAY have been using street tires, not mud/snows.