I bought an extra differential from a member of my local club (Capitol City Rockets) it's a 342:1 w/posi nicely powered coated and after asking around I decided to go from 323:1 to 342:1 I really don't know who rebuilt it but it was nicely done and it could have been Brian Trick (I believe he is also a member here) as it was a restoration shop in Frederick Maryland that was restoring his 68 442 resto-mod. I have a ways to go before I get it back on the road. I learned a long time ago that a real clean surface always gives a great seal and preparation is 75% of the work.