Is this an Eaton (pretty sure)?
Yes.
What specific name do they call it (10 bolt 7.5, 8.5, 8.875, none of these??)?
Eaton HO72. Eaton HO50 is the 3/4-ton. Primary difference is brakes, though the HO50 is usually 4.57 gears.
If not where can a 3.XX gear be bought?
I've heard the talk, but never seen proof one exists. The 4.11 is rare but does exist.
I have to think that a different rear (like a Dana) would probably be cheaper than changing gears,
Swapping to 4.11 would likley be your cheapest option. Getting to 3.xx I agree an axle swap would be cheapest and perhaps only option.
but then how much of a struggle will I have with brakes?
Choose a drum brake axle from a similar rated truck and if the brakes on the replacement are any good, then just hook them up and bleed them and go....
Dana 70HD is pretty common and has brakes about the right size. Some of them will be far too wide. GM 14-bolt is also common under similar rated trucks (I think often the heavier rated are Dana's, but I con't know that with certainty). Unless you're putting disks up front I'd stay drums in the rear. You'll have an easier time getting it to work right.
I've got a GM 14-bolt with 3.42 gears under my 1-ton and there is a 3.21 available with lots of options the other direction too. I don't think the Dana options are quite as highway friendly which is consistent with the applications of the two axles.
What year is your truck, and what motor do you plan to run? My 14-bolt came to me under a '49 1-ton with a 216. The guy I got it from said the tired 216 would hardly move the truck with the 3.42 gears and that was why he had parked it and eventually sold it.
