Perfect timing. I just installed a retro sound Daytona for my soon to install 70-77 dash, fits awesome. I ordered with black knobs and then ordered a set of chrome knobs, using the chrome for the rear knobs and the black for the main knobs. Will post pics later tonight in my test 77 dash as well as in my current 81. I have an 81 dash for now and it still looks good though it is not intended for 78-81, it works with repositioning the knobs.
As b_hill_86 noted I would do the the same 6x9 in back (I like the 3 way style to get most sound out of them) and the speakers for the center speaker. I have am 81 dash luckily I have the two smaller speaker locations on the upper metal dash, otherwise I would do the same with the center speaker. Others have some speakers on the door panels and center console. It is your car, do what you want but I personally like when the car looks period correct as much as possible.