Another option.
https://www.classiccarstereos.com/19...ck-panels.html
The rears in your truck ,I am going to guess are either 6x9s or 4x10 That someone dumped in the cab corners.
If you are into the junkyard crawl, many early 2000's g.m. full sized suvs have fairly nice 4x10's in the rear.
A set of 6.5" seperates that you can put the woofer where the speakers in the back corners of your truck now are, and the tweeters, up higher near the top edge of the seat. will sound 100x better. and you don't need costly ones.
The kick panel location gives you good staging instead of the under dash set up, that I will assume the front of the speaker is facing the floor .