The 14FF only came from the factory in the 8-lug configuration.
The 14SF came in 8-lug and 6-lug varieties. I also believe a few 5-lug versions were found here and there (such as on the 454SS pickup). I don't think the 6-lug version was available until the "new" style pickups w/ IFS were introduced in '88, the 6-lug was used in the light duty 2500 (3/4 ton) versions while the heavy duty 3/4 tons used an 8-lug version. A few 1500 (1/2 tons) with some combination of trailier towing packages also had 6-lug 14SF's.