I did the swap from the original closed driveshaft to a F**D 9 inch. Used the Mopar spring perch from Jeg's. Didn't have to drill any holes. Used the holes that were pre-drilled in the perches. Even though it made the rear end set ahead about an inch, you couldn't tell it.
All the original springs and shock mounts are re-used, but you will probably need different U-bolts.
