I can tell you that factory speakers I beleive are all 2-ohm based on common ground used in the vehicles. I replaced the four factory speakers with MB Quart speakers and hooked in a 8-inch self-powered Bozooka tube. This truck has a small cabin enclosure and a small bass tube does wonders for sound. I recommend rewiring around the factory amps and going direct to your new head unit to acheive better performance and less buzzing-popping etc. Oh yes, once you rewire, your ohms should advance to 4 versus factory 2 ohm load based on new floating ground versus common ground.
Gee, in short, any speakers you choose, regardless of new head unit or not, will do a better job IMHO.
BTW, I left the factory tweeters in pillar, yanked the two 6" subs and amps. Also, you are very limited in depth for both front and rears, so 4" is the best unless you plan to redo the bottom door panel pockets to gain more depth for speakers, but water will be your issue if that is your choice.
Good luck.
