radios

No, all radio's are not generic.  I have more than one AMC car and have not found any two that have the same radio. The are all 1970 or newer. I do not think that today there is even a radio made that fits into the AMC car which seemed to in general have an odd sized radio.  Another problem I have come up with is that the face plate, for lack of a proper word, the part of the radio that is seen on the dash board will have a slightly trapezoid shape rather than rectangular
I am having a bit of a problem coming up with one for my 1976 Hornet and to date have found nothing that fits. The last radio I bought was about 2000 or so for my 1980 Spirit and it fit the hole but the stems for the knobs were a problem.
And I am unable to locate in your normal radio sources one that is even close to correct for either the Hornet or the Spirit.
I have bought speakers from here and you might want to look to see if they can supply you with a radio.
http://www.onlinecarstereo.com/
Speakers such as these:
http://www.onlinecarstereo.com/products/15/Car_Speakers/Full_Range_Car_Speakers.aspx
do make a difference.  A lot more so than can be imagined. I have replaced the ones I used in the Back of my Spirit (a hatch back with a cargo area) with something from here and used only rear speakers rather than cutting the upholstery up on the doors to install them.
The decision of course is yours, but I am not ready to cut up irreplaceable door upholstery to put speakers in. When I first installed the radio I chose to mount the front speakers in such a way that they did not damage the upholstery and the end result was not very satisfactory.  So I removed them completely.
I am not working on the size of amplifier needed and the location in the car it can be mounted with being obtrusive to drive a pair of tweeters for the front of the car.  Tweeters can be buried pretty much anywhere but in general the average car radio is not powerful enough to drive them.
In any case a speaker with a built in tweeter and cross over is a bit more money when used in the back of the car but the sound quality is orders of magnitude better than what I had before.