Here's what I have: 87K5 305 465 208 4" lift 35" tires 12 bolt rear I just swapped out a 10 bolt for a 12 bolt and now I am wondering if my drive shaft is long enough. The 10 bolt sat foreward about 1.5 inches closer than the 12 bolt. I think the drve line is stock so it might have been too short for the 10 bolt as well. I am going to get a Suburban driveline and have it cut down to the correct length. Here's my question: What formula should I use to determine the correct length of the drive line?