Well after trial and error with the rear axle seal and coming to the conclusion that it's f'd and will forever leak I have decided to change the entire rear end and have a few questions.

I know that you can use a rear end from any ranger/Mazda from 93 to 09, which I have an 02 myself, but do I have to get the same gear ratio that I have now being an open 7.5, my truck is rwd btw, or can I possibly get something better like an 8.8 l/s, and if I can what would I have to do to acomidate a new rear end with a Limited slip dif or just an open 8.8

~Thanks

Since you are talking 2WD the Gear Ratio isn't as important as a 4x, if the replacement axle is in good condition, just bolt it in and get going.

If you know your existing Gear Ratio in your truck, it would reduce the work to have the gears already installed in the replacement axle.

IF you can get a Ranger 8.8 to replace your existing axle, that can only be a plus, some extra work if the axle is from an Explorer.
The Explorer 8.8 are usually 4.10 gear ratio, Disc Brakes, and 31 spline but require mods to fit.
My '03 8.8, 28 spline housing had 4.10 gears, I swapped it out for a '02, 31 spline Axle with 4.56s and the same type brakes.

Things to think on !

+1 ^^^

You can use Ranger or Mazda B-series, 1993-2009 axle as just bolt in
I would get new u-bolts and nuts, they are cheap and old rusted ones can be a pain to thread, and you can then just cut the old ones off

Get used axle WITH brake drums, as there were 9" and 10" models, that way you don't have to look for parts, just redo the brakes if they need it

Ratio is drivers choice but speedometer is programmed for current ratio so changing it will mean speedo/odo will be off, but not much, computer(2002) can be reprogrammed for new ratio just like it can if you change tire size(diameter)

8.8" L/S would be a good upgrade, you will pay a bit more for L/S but in my opinion its worth it
There is an additive needed in L/S differentials if you change the oil

Many 4x4 Rangers came with L/S rear axles, not all, but good bet it will have L/S
There is no difference in 4x4 or 2WD rear axles

How would i get it reprogrammed

Also would it be a good idea to replace the axle seals and yoke on the new(old) rear end as preventative maintenance?

Ford can reprogram it, or some auto repair shops that have Ford software can do it, never had it done so can't say how much they charge
And you would want to SEE how much its off before doing that
Ford allows 5% deviation in speedo/odo calibration, lol, which is +/- 4MPH at 70MPH
So new ratio may make it more accurate, lol

You can also do it yourself with Forscan software and USB/OBD2 cable

Unless the replacement axle shows signs of leaking I would leave it
Its actually easier in most cases to replace axle seals and bearings with axle mounted in the truck, only the refilling part is easier with it out of the truck, lol
But just an opinion

I planned on taking of the axles anyways so I can put the 10" drums I already have since the axle I got came with 9" drums so I rather keep my better ones, and I though of putting new seals since I'll have access to them.

Well, yes, if axles are pulled out then why not replace bearings and seals

Not sure how to reprogram the Speed-O but when I changed my '03, 4WD, to 4.56 gears from OEM Stock 3.73 gear-ratio (GR), with 33" Tires, my Speed-O was 3-4 MPH Higher than the 3.73 GR, not a lot of difference.

If you are planing to run 4.88+GR with 37" tires the Speed-O will be off by more... but I don't think you are planing on those gears or tires.

First find out what the gear ratio is for the axle choice; then start thinking what you may want to do.

My thinking on OEM Gear Ratio is... the OEM Gear are a compromise at best, trying to get just the right MPG, not taking into consideration what the truck will be used for.

What is your OEM Gears for the truck ?
Look for a higher numerical gear ratio if you want more power than you had, and go to a lower numerical gear ratio if you want better MPG... don't go too low on the numbers, expecting to get 30 MPG... doesn't work that way.