I just did a little digging in the forums where I had posted on this subject back when I was looking. It's been nearly ten years. Not quite.
I misspoke earlier. My first set, I think actually did come from Tom Myers, and at the time he said it was in a early 60's truck, I think 62, maybe 61... I can't remember for sure now. The post I found from myself stated that the second differential came from a 63 Chevy 1 ton, and it had been completely reconditioned by the rear end shop I bought it from. The PO was swapping for a Dana with a posi. My 4.11 has a Detroit Locker. I paid $650 for it and had about a 14 hour round trip drive. That was approx. 2006.
In any case, I digress, because the conventional wisdom at that time was that the early 60's trucks were not born with these gear sets. I can't confirm this personally because of what my experience was, but supposedly the 67-72 carrier is the one that accepts the 4.11 gear set. The telltales guys have stated is to look for big block automatic trans trucks with coil springs. They generally have the 4.11 gears. I don't have time to search for casting numbers but I know there are a few that have been documented. I'd go get the numbers off of mine for you but the truck is in storage several hours drive south of me.
