I'm pretty sure mine are not HD 60's after seeing those pics. As I stated before, the 69 housing has a couple extra gussets on the case near the pinion where the 75 housing does not. I will take a couple pics when I get over to my Dads place where they are currently setting. (To heavy to justify moving if I don't need them quite yet) Interesting info though. Sorry to post jack. My apoligies.

On the earlier castings, there were quite a few different pcs that had small ribs here and there.
as time progressed, the castings got a "cleaner" appearance.
No doubt been counters trying to save money during casting process.
From looking at the way the old ones were gusseted, you can see where engineers must have felt there were areas that could use additional support, hence the reasoning behind using the Dana 60 HD.