lookes like a ford 9" turned upside down????)
Nope. It's a GM HO52 or HO72. I know because Bob has a whole row of them behind his shop
. Most people call it an Eaton 10.5", but it was actually made by GM. There is a lot of Info on it on 67-72chevytrucks.com & Pirate 4x4. It shares alot of similarities with the GM 14 Bolt rear end, except it has a removable punkin like the 8-3/4" and 9" Ford, which is a lot easier to work on. The Dana sucks with the adjustment shims. Don't try to fix one in the field. And it only has 2 spider gears.
The GM HO52 or HO72 came in 1946-1972 Chevy and GMC 3/4 - 1 ton pickups. It looks alot like a 9" Ford, only bigger, stronger, and a less severe hypoid angle (less HP loss). It has a 10.5" ring gear (actually closer to 10") and "4" LARGE spider gears.
The "4" large spider gears are a must when using steering brakes. Some are using 9" Fords with NASCAR 4 gear carriers, but you can't run on the back side of the ring gear very long.
With a 2 gear transfer box like the Casale, the driveshaft rotation into the rear end is still the same (clockwise). With a 3 gear transfer case like the NP205, you are turning the driveshaft backwards (counter clockwise), so you are driving off the back side of the ring gear. Most rear ends won't run that way very long, but the HO72 handles it very well because it also has a ring gear Load Bolt. The HO52 & HO72 came with both 2 & 4 spider gears, with and without Load Bolts. You want the one with 4 spider gears and a Load Bolt. Best years are 1968-1972, next would be 1961-1967.
One interesting thing about the HO rear ends is that the bolt pattern is symmetrical. You can turn it 180 degrees and it still bolts up. You can also remove the rear cover, and it will bolt on the back side in either direction too. And if you want to go from the original 17 spline axles to an updated 14 bolt rear end axle with 30 splines, all you have to do is swap the side gears.
I wanted to narrow my HO72 a little, the cheapest way I could. One axle is 6" shorter than the other, so I got another short axle and cut the long side of the housing 6". Now I only need to carry one axle as a spare.
More info coming. I'm am building a 2001 Dakota (Does an "AN" body count) with a blown 440, 727 4x4 transmission with a bolt on NP205 rotated 1 bolt hole so the front output is almost straight down. I was originally going to use a short tailshaft truck 727 and a Divorced NP205 transfer case, but the married transfer case seems easier for now. (see 1st pic)
Hope this helps,
Speedy Lee