So I have 15 inch rims on my 99 Ford ranger right now and I’m looking to go up to twenty inch rims and they came off a 2001 ranger I was wondering if that much of a difference between the 15 inch rims and the 20 inch rims would that hit the suspension or anything. Or would they be hitting the inside of the wheel well I’m just wondering if the suspension would be able to fit them

 

It depends on the aspect ratio of the tire.
Without lifting the truck's body, you'd need to go to an unacceptably low-profile tire on a 20" wheel to fit your wheel wells.

 

the tires that are on those rims and the ones I would put on it are 245 45 20

 

Assuming the stock tires on your truck are 235/75 - 15

the outer diameter and width are almost the same, so they shouldn't be a problem

 

I believe I have 225 75 14 right now

 

And what about the offset