What wheel bolt pattern are you talking about? I have seen the 14BSF come in both in 6x5.5 and 8x6.5. I not sure, but I think the 14BSF from 81 to 87 models only came in eight lug while the later models came with both. My mom and my brother's truck both have "light duty 3/4" exended cab 2wd trucks (91 and 93) and both trucks came with 14BSF with the 6x5.5 bolt pattern. My dad once had 2wd 96 "heavy duty 3/4" with a 14BSF with the 8x6.5 bolt pattern. I can't see the the reason why you want to replace the 14BFF with a 14BSF. Unless you are replaceing a 10 or 12 bolt, or maybe 14BSF to a 14BFF.