The Wheel data spreadsheet I use states that DF is:
1967 - size 15x6 JK for Camaro Z-28 and coding for these wheels began on 3-1-1967.
These wheels use 5 bolt pattern, 4-3/4 bolt center, 7/16 bolt size, 2.783 center hole, .62 offset, 13.156 rim inner dimension, welded construction, and manufactured by Kelsey Hayes.
The database also says they were used in 1968 on Camaro Z-28. So I assume that it was a general production wheel.