Lets clear up all misconceptions...
To my knowledge a 14bFF can't be turned into 6lug economically.
14bSF come in 3 different lug patterns: 8 lug (most common), 6 lug, and 5 lug (very rare). The 14bsf first came out in 81 and was unchanged until the new body style trucks in 88. And in the original 81-87 run, the 14bsf is a dirrect bolt on, but only came in 8 lug. The newer style from 88 and up was available in all 3 lug patterns. 5 lug only came on the 454SS pickup, 6 lug came of some heavy duty 1500s and some light duty 2500s depending on the trucks GVRW rating and I believe the 7200lbs rating is what you need to look for, the 8 lug version came in most of the 2500s and some 3500s. The newer style will not bolt directly in because the spring perches and shock mounts are in different locations. So you can just cut them off and weld on new ones to the correct placement.
There is more info, but I don't have the time now to type it all up. So I say do a search on the 14bSF and 14bSF 6 lug conversions.