I swapped in a FF two months ago. I was fortunate enough to find a beat up dolphin for $500, which allowed me to pick and choose what parts worked best. The RV I am rebuilding is an '83 the donor vehicle was an '84. The shock mounts were not the same between them, so I used the '84 u-bolts with the '83 mounting plate, I had to break out the cutting torch and egg the holes out 1/4" to fit the larger u-bolts. The drive shaft flange bolt patterns were also different, again when I replaced the u-joints I swapped them around and it worked great. Those were the biggest obstacles I faced in doing this swap. I have put around 2000 miles on it since.