Might want to check the engine casting numbers on the passenger side of the block. You may very well have a 235 instead of a 216. 235ci engines were standard in all 6000 series(6100, 6400, & 6500)trucks. Coupled to the fact your truck has a 2 spd rear axle has me leaning towards a 235. I'm curious as to what you do have. Since your truck is a "Rare" special order 15000lb. gvw truck.
