Upgrading Sound system in 4th gen

I still have the non functioning AM radio w/ upper rear door post speakers in my '76 Elky & I want to install a moderatly priced system. I have found several factory AM/FM systems at a local junk yard (one is in a '77 Cutlass). What year GM radios interchange and fit in 4th gen dashes? Do you need a special factory harness to install these OEM sterios? What speakers should I use to fit behind the upper rear door frame trim? Thoughts?

Please don't quote me (and someone please correct me if I am wrong) but GM radios were pretty much standand for any model, any year, in the 1970's

should be standard. if your going to the trouble I would try and find an aftermarket radio. I think 4x6 or 3 1/2 should fit where you are talking. I used to have a pair of 3 way 6x9s in truck boxes behind the seats on my 77 and will probably do the same on my 74.

I took my old in dash thing out and installed a new CD Player with AM/FM etc... I put in speakers in the ear boards. Someone had stuffed a bunch of paper, news paper, in the holes for the rear speakers in 87. I know it was in 87 because the News Paper had the date on it. Some ants had made a nest in the paper. The first time my wife took a ride in the Elky with me she pulled out the seat belt and within just a minute or so she had ants all over her!

I know that this truck was in service and being used up until about a week before I bought it. I have no clue when the ants got in or had time to nest. We went home after that and I sprayed the cab with bug spray. That was before I re-did the interior.

I looked around before I did that and there are some options for installing stereos. The El Camino Store, EC Parts and J.C. Whitney's all have stereos that will fit well in the holes as is and some even have a controller so that you can install a CD Changer and still keep the type stereo with knobs.

The CD I put in was pretty cheap but it works well and it makes enough sound for me and I like the way it sounds so its not a big deal. I installed some cheap speakers too. I don't always listen to the radio or CD, Cassettes. Most of the time I like listening to the truck while I am driving it around. Especially on the freeway.

This probably sounds strange but I'll listen to it more as I get more use to the way the Elky sounds running. I don't have enough time in it driving it to be completely comfortable not listening to the engine and transmission. Maybe I don't trust my own work.