What size speakers go in a 1998 ford mustang gt with match audio system it's a 2 door with back seats?

I see some that say 5 1/4 s one say 6x8 rear and front some mix and match with 5x7 i just want to know what ones go where and what size is the tweeter

Yes

A) It's a MACH sound system, not a Match sound system.

FAIL

b) Apparently you also suck at internet searches as much as spelling. Here: https://www.crutchfield.com/S-PesHK2CQmCH/learn/reviews/mustang_install.html

6 * 8 and 5 * 7 are the same thing it just depends on the make of car some call them 5 *7 other prefer 6 * 8. You can actually fit them in both door panels or if you want you can put them in the rear. There are only 4 speakers in my 03 v6 Mustang, 2 door panel speaker and 2 rear deck speakers. Hopefully the helps but if not go to the Crutchfield website you can put your make, model, and year of car there are plenty of options that show if it is compatible or not with your car. The reviews are helpful as well. Another quick thing is their customer service is extremely helpful with solving issues to your specific case.