Thanks guys, lots of good feedback as usual. I'll probably put a 'moderately' loud exhaust, definitely not stock so the points about the outsides contributing little volume are helpful. Back in the 70's I just used the two 6x9s in the back of my Roadrunner and I guess that could work in the Barracuda, but I would like to have some front speakers without cutting the kick panels or something similar. I may go with the 3 speaker dash and just see if there's maybe a more modern small speaker I could fit into the original openings, and go with the 6x9s in the back and call it a day.
Thanks again, Jim