[jocko]

5 on 5 is not 6 lug - it means 5 lug nuts on a 5" bolt circle. You would need 5 lug wheels with this setup.

Edit: just to clarify - half ton trucks were 6 lug thru late 60's - early 70's were 5 lug (only 1/2 tons that were 6 lug in early 70's were 4x4's)
I don't recall the exact year of the changeover, but you fall into the same category as 60-66 half ton trucks with your 1/2 ton 6 lug life.