16x6.5, 8 lug made by Kelsey Hayes. Should have a small "KH" stamped somewhere on the rim, usually near the valve stem. Painted off white originally. OEM on the 74-87 C/K20 & SRW C/K30 ..and a little longer on 3/4 & 1 ton vans/burbs. 73 & earlier were a bit narrower at 16x6.0.
http://67-72chevytrucks.com/vboard/s...d.php?t=621735 (conversation I had with myself)