This is how I did it.
1. Seal the rubber to the car.
2. Put Vaseline in the track.
3. Heavy strong string in the track.
4. Put glass in and pull string.
I've only done it three or four times over many years but was always easy.
I had something like this in my 65 Belvedere.
http://i.ebayimg.com/00/s/OTAwWDEyNjM=/z/OJEAAOSwI-BWLjw3/$_1.JPG
Seriously there are retro radios that you can put in that will fit. I think some will run a CD player that's mounted elsewhere.
I had a 360 with 308 heads and one head developed a crack near the exhaust valve seat. Must be a water jacket there cause it would eventually over heat but no water would leak. I'm thinking exhaust gas got in through the crack heated the water and over pressurized it.
I have a 66 with 408 and w2 heads. I bought Hedman fenderwell step tube headers for a 67 and up and w2 flanges to weld on. Have not installed the headers yet but felt like this would be the easiest route.
Does anyone know how much tighter? In inside and outside frame width differences? I'm doing close to the same thing but with fenderwell headers for a 67 and up.