Other than looks, will a 2005 bumper (bottom) fit my 2000 Ranger? (top)

 

Yes bolts right up.

 

yes. should bolt right up

edit: josh beat me to it

 

Also you can add a Mazda B-Series Bumper with slight modification. I think they look better and are rounder. The Mazda bedsides are slimmer so the bumper pad actually touches them on a Ranger. You can take a Dremel and cut off about 1/2" on each side and you will have no problems.