there are some installation kits available that have a perch with a hold drilled right where it should be which lines up everything very well- I just put one in- had to have them welded to donor axle but it wasnt too hard. the kits are around 140.00 - chevy duty sells them - they also come with shock mounts on the plates which converts the lever action to the better functioning piston type "modern" shock...
good luck!
