I think they are like 3.5 in the dash, it's a horrible setup, in my 71 I have custom pods to place 1in tweet and 3in mid in around the kick panel, and 6.5 mid bass in the door, for a better system, modifications must be done
check crutchfield.com They usually have just about any vehicle and exactly what will fit or need to be modified to fit.
This site has some kick pods if you don't want to cut open your door panels/metal Q Logic 86-95 Toyota Truck 6 1/2" Custom Speaker Kick Panel - QL-K4002C-86-95-TRUCK
I have a set of those that I plan to install. They do look fairly ugly and are wildly expensive. I hope I'm not disappointed with the sound.
Our 69-95 pickups have great footwell room for kick panel staging, I think it should sound good, just remember to reinforce those plastic panels with dampening product if you buy them
I did a 8" midbass in the door, with a four mid in the dash, and a 1" tweeter in the upper door corner, works great!!!!!
I'm very curious to see your door as well... I'm still deciding between the SLS8 and RS225 but I do feel strongly that I want to put the 8 and 4 in the doors and the tweet in the dash, firing at the windshield. Could you plllleaaase post pictures?