70 is a 70, usually has 3.5" axle tubes
70HD is like a 70, uses the same gears, but with larger carrier bearings, 4" axle tubes, and spindles sized more like a Dana 80
80 is an 80, bigger then either 70 or 70HD.

I've been told that the 10 lug hubs for a 70HD won't interchange with an 80. I think a search of this forum will reveal the details, I forget exactly.

I've never seen a 70 with the 10 lug hubs.

On a completely different note.
You were looking for folding steps earlier, here they are: https://www.surpluscenter.com/item.asp?UID=2468021821383980&item=1-3297&catname=

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-