HA! Found the info on paint codes. Your post jogged my memory on that one. It was about 2.3% of production for the '72 Valiant and Duster. But that's total production, the 340 cars may have been a little different percentage-wise.
And in general, if information like that is what you want Hamtramck-historical is where you'll find it. @Alaskan_TA runs the site and knows a lot about that sort of stuff as well, he may be able to shine some more light on the production numbers. But as I said earlier, I'm pretty sure that you won't find a break down by options beyond the 340 and possibly the transmission, it comes up all the time and the records just don't exist anymore. The 1970 Hamtramck Registry Home Page