I am considering doing a 4x4 conversion to my 2000 2.5 2wd. after doing some research ive come up with nothing. I cant figure out what transmission i would need for the swap because (correct me if I am wrong) there was never a 2.5l 4x4. Has anyone else done this? I hope this isn't a stupid question, but any help would be appreciated.

 

Ranger 4 cyl(2.3l/2.5l lima) with 4x4 was last offered in 1997 I believe, '98 was the start of 3rd Generation Rangers.
'83-'91 is 1st generation('89-'91 is 1.5, lol)
'92-'97 is 2nd Gen
'98-'12 is 3rd Gen

So your 2000 Ranger is 3rd gen and swapping drivetrain parts over from a 2nd Gen could be a problem.
Trans wouldn't be an issue, '92-'97 4WD and transfer case from 2.3l or 2.5l would bolt right in, front axle would be the hard part.
You would need to know what suspension you have now and then see what you would need from donor 4WD.
Read here: The Ford Ranger Front Suspension.

The 4WD control panel, wiring and module would need to be added, or you could just use a Shiftster to switch transfer case.
And you would switch to manual hubs no matter what, Ford Auto hubs never worked well.

In my opinion it wouldn't be worth the time and cost to do it, one of the reasons the Lima 4 banger was dropped from 4x4s in '98 was because they were marginal for power with extra weight in 2nd gen, 3rd gen 4x4's were even heavier so instead of dealing with the complaints they just dropped it as an option.

Selling your 2000 2WD and buying a '96/'97 4WD 4cyl would be a much better idea IMO, then spend the money on fixing it up.

 

You would also need to do a frame swap or SAS