i dont know if it is difference between a stepside bed or fleet side but the rims off my 99 F150 Flare with the 9.75 rearend have a smaller bolt pattern than the 99 F150 fleet with the 8.8 rearend. found this out when a buddy of mine had a flat and couldnt use my spare. and yes im confused because u would figure the larger rearend would have the bigger bolt pattern. hmmm go figure

 

yeah i cant remeber the stud size but actually at one point they had the same size studs then a few years later they upgraded to a thicker stud. It doesnt have to do with the rear axle size but the year of the truck