If it were me...

33's I would do 4.10
35's I would do 4.56 (especially if you are towing a lot)

IIRC, you can go all the way up to 4.88 without changing the carrier in the diff.

The other questions? I am not that knowledgable about varieties of the Rams yet.

 

As above. I've got 4.10 gears with 33" tires (up from 3.55 factory) and it works well. 3.92 was an optional gear ratio (in the 1500 series at least), and I believe 4.10 came with the off-road package.

 

Also one thing to consider is if your truck is 4wd. You need to regear the front differential the same as the rear. You can do just the rear but then don't use 4wd until you regear the front. You could go up to 33" tires and run it with the 3.55 gears for the time being. Its going to be pretty doggy and harder on the trans.

You should update your info to include where you are from. There might be a knowledable member near you that might be able to help you with regearing.

Setting up a differential is definitely an art. Takes patience. "Good enough" is nowhere near good when setting them up. I also second 4.10 with 33" tires and 4.56 with 35"tires.

Could drive the truck as is, and save up for a lift, tires and gears, then buy everything all at once and put it in.

 

I plan on doing them together. I just updated my profile, I'm in Omaha NE.

Was there a 4.10 rear end that came in a 1500 factory? And how hard would It be to find one? Or at least one that would fit and still has 5 lugs?
Same with the 4.56?
Or to get it do I just have to regear?

 

Off-Road Edition trucks came with 4.10 gears, and it was also an option. They are rarer than hens teeth though.....

Also, keep in mind, if you pay someone to regear your axles, you are looking at 1500 bucks or more. (parts and labor, assuming 4x4) Not a cheap endeavor by any stretch of the imagination.

 

What did the 2500 v8s come with? 4.10s?
V10s?

 

Mine came with 3.55's...... Of course, the 2500s have D60's in front, and anything from D60 to D70 in back, and they are all universally 8 lug. I have seen a couple 2500's with 4.10s, but, they seem to be rare too.

 

if you have patience and quite a bit of time you can do the regear yourself. find threads on the interweb and read up on these axles. theres a couple special tools you'll need which you can purchase OR with a little bit of skill and time you can make.

search for the thread, "my 4.56 gear swap." theres a lot of good information in there on the special tools you will want to make or purchase. this will be a good start for you. search specifically for information on the chrysler 9.25 since it's a little different than ford and gm.

for the front axle you'll want to make a differential case spreader. again, you can buy one but they're not the cheapest.