Sounds like you already got the ball rolling.
However... if you had the axle with the factory perch's still on it... it is just a simple measurement off the factory perch's to set the new perch's for a YJ. No need to hang, no need to plum bob, no need to measure off the backing plates. You simply measure outboard 9/16" each side and set your new perch's there. Simple.
'05 LJR, 6sp, RC long arm w/MC 6" coils, 5.13 D44's w/chromo shafts, MetalCloak fenders/sliders/body armor, 37x12.50 MTR's, Warn 9.5, RockHard swing out w/full spare. <><