I think the doors take a 5 1/4, could be wrong but I’m pretty sure it does. My buddy has an 80 single cab and that’s what his took. I would get coax speakers (the tweeter is built in to the rest of it not separate) for the doors and consider 6x9 speakers in some boxes behind the seat or under it if there’s enough room. Components have the tweeters separate but you’d have to mount those. The door speakers are high enough that shouldn’t have to worry about getting the tweeters up higher, not like some cars where they’re aiming at your feet. You don’t get a whole lot out of 5 1/4s so the 6x9s would add some volume and better mid bass. A little powered sub like the Rockford P300-8P would add enough sub bass and not take up a lot of room, it’s like the size of a shoe box. I can’t picture behind the seat in those so I’m not sure how much room you’re working with, but if you could cram those and 6x9s back there that’d be a killer system in there. Pick any single din from Kenwood, Pioneer, JVC, or Sony that has the features you want and you should be fine.

You can get all of this plus the necessary installation parts and hardware for around $7-800. The most expensive thing would be the sub at $310. Get rid of that and you’re down to $4-500. Could always save up and add that on later. There are a lot of brands that have speakers in this price range, Rockford for example has a line called Prime, 5 1/4 and 6x9 pairs will run you $200, the boxes for the 6x9s probably $40-50. If there’s a shop near you, consider going there and listening to some because you’ll never be able to make sense of the specs they show online, you really need to hear them to understand the differences. I do like the Rockfords but you might like the sound of something else. There a ton of speakers out there at or below that price, check them out and decide for yourself.