I have them on my 69. I have the JCL baffles just waiting to go in. Although the car sounds cool, it lacks the polished refined sound of a good under body exhaust with high quality mufflers.
The sound is not too bad. It is hard to have a read deep conversation inside when going 70 mph, and a stock radio would never keep up.
It is very hard to hear/talk on my cell phone at 70 even with the top up, but it can be done.
I also installed the hoopty stereo so that I had the option of going deaf by cubic inches, or by cubic subs.
I don't know about your small block, but one cool thing about the hookers is my car sounds like an entire pack of harley hogs coming at you. In fact, most of my friends have told me they thought the Hells Angels had pulled up in their driveway when I come to visit.
The sound is unique, loud, and --- well, it is one of the few cars in the whole world that you can get away with doing it!
I plan on using the JCL baffles with the front cap in place. Removing it is known to net a few more ponies, but I too am concerned about extra noise.