Peter, Casting number on the center section should be 3859140N for it to be a 1965, 3875745N for a 1966. As far as the value for an empty housing, I'd have to say around $200.00 to 250.00 here in the U.S. New Zealand could be a different matter all together. Between new axles, gears, posi, pinion flange, bearings/seals etc. plus professional assembly you're looking at well over $1300.00 complete. If you look on eBay, that's about the going price for a complete quality rebuilt 12-bolt from someone you can trust. The last 1966 12-bolt I sold was an original 3.73 posi rear which had a cracked posi unit. I installed a new eaton 3-series posi unit, cleaned, painted and reassembled it with new bearings and seals, sold it to a fellow from western New York for $1000.00 and at that price I made no money at all.

 

Dave, thanks for the info.....yip the diff is a '65 model and the numbers do match. Next question: how rare are these diffs......?

 

Sorry I can't help with your question Peter but I was wondering what part of New Zealand you were from? I have family over there. I also see you just registered the other day. Welcome to TC!

 

I don't think there is any way of telling how rare (or un-rare) the 1965 12-bolt is, since there generally aren't available records for these parts.

The 12-bolt was a HD item not a performance item, and as such, would have come with the higher HP engines.

Obviously the Z16's had them (but special versions), and most likely most L79s and possibly most other 327/4-barrel cars, especially with 4-speeds. Obviously, they are not as common as later years.