Yes I have had one for about 6 years in a 69 convertible. I have the Secretaudio SST 200 watt 45X50 system. I installed a dual voice cone speaker in the front dash. I have the two underseat speakers but they will not fit under the front seats so they are on the floor in the back. I pulled out the ash tray and installed the controller over the opening using the ash tray bracket holes. Fit rather nicely. The stereo is hung under the dash over the steering column. Plenty of sound even at highway speeds. (Note I have a fairly quiet exhaust system. )
If I was doing it over I would put in new kick plate speakers and skip the underseat speakers.