12 bolt width/8.5 10 bolt posi questions

[69Z28]

How wide is the Camaro 12 bolt backing plate to backing plate? I measured mine at approximately 53". Is this correct?

Also, I have a 8.5 10 bolt posi that measures approximately 56" backing plate to backing plate. Could this be for Chevelle possibly? Or 70's Camaro? I have this coil spring 8.5 10 bolt with a traction lock posi (based on info I received from BIGGEARHEAD last year) that I have no idea what it belongs to. Been surfing the web since 3 AM this morning trying to find info on it, but kept coming up facing a stone wall. I can't tell if it's a dated 69 unit or a 79 unit. Posi unit works fine. Based on the date of the differential H 15 9 and the carrier 410409 N dated H 2 9 and the ring gear part # 1 GM 1252065 17 41 dated 9 79 I can't tell if I'm coming or going. The passenger side tube has what may be a 7 but only has the bottom leg then KA   G267  1. I sure could use some help on this. I plan on just selling the posi unit but if the housing is a good needed housing I would rather see it go to someone that needs it.

Thanks,
Gary

[1968RSZ28]

How wide is the Camaro 12 bolt backing plate to backing plate? I measured mine at approximately 53". Is this correct?

Yes, that is approximately the measurement on my car.

Paul

[hotrod68]

The '69 10-bolts were 8.2" ring gear, so you have a '73-up rear. If I remember right, after '72 the 12-bolt was gone and all the axles were 8.5" after that. It couldn't be for a '70s Camaro--they were all leaf spring cars. My 2 cents and good luck!