I located some of my notes from my last discussion wtih Bob Christensen re the Service Package rear end. It has been many years since Bob owned that car, and raced it in T/A and IMSA, but his memory is fantastic. I talked to him 3 or 4 yrs ago by phone (he now lives in KY). At that time he told me the standard 12 bolt rear Posi Unit had a breakaway torque of 50 ft lbs, whereas the Service Package Posi unit had 4X that amount (200 Ft-lbs), using 22 plates and larger heavier springs in the unit. He ran his own '69 Z28 from '69 to '74, in regional SCCA, T/A, and IMSA GT, and also ran the Bolus/Snopes Camaro with Bob Mitchell (another Huntsville, AL racer/engineer). They finished 4th and 5th respectively in class at Sebring 12 hr race in '71. Bob Mitchell finished 2nd in class in '70 at Sebring. They both were very good engineer/racers and raced and competed for close to 10 yrs from late '60's to late '70's. Both bought new '69 Camaro Z28 cars and immediately converted them for competition. I have a few parts from Bob C's Z28 (the SP rear and the original 1st day takeoff exhaust manifolds..
. I'd love to flesh out the specs on those service duty rears if anyone else has any info. The one I have needs to be setup - has 4.11 gears and the original posi and two sets of axles and caliper mounting brackets, but no brake parts. I have mid 60s' Corvette brake parts that I would like to build up the rear as close as possible to original spec A(with the parts I have).