I know I am supposed to have matching tires, but do all 4 have to match, or do the front and reads just have to match each other? This is my first 4x4 so I’m still trying to learn the basics.

Also does using fix a flat screw anything up? (I seem to be missing the underbody spare tire mount)

It’s a 1998.

 

Ideally, all four tires should be an exact match. Realistically, you're probably ok if they're all the same size (actual dimensions, not just what's marked on the sidewalls). I would try to at least match pairs, though (front and rear).

And using fix-a-flat is a great way to make your tire guy hate you. If you must use it, at least warn the person who's going to break down your tire and do a "real" repair.

 

Yep, agree with Tom. Match what you can, if not, make sure they're the same size. I've never used fix a flat, but I've also heard tire guys hate it. If you have TPMS, it'll mess up the sensors, also

 

If You intend to use 4WD, the diameter of the tires must match. Otherwise, You put a risk on Your transfer case.