Ran across this thread while looking for paint info on Google, but thought I'd chime in and correct some info.
The roots of the Road King is the Electra Glide, no matter how you slice it. The frame up until 2009 was based on the most current FLT swing-arm frame that started in 1980.
The Bat Wing fairing did not appear in the '70's, but three years earlier in 1967.
As far as looks are concerned; The style of hard bags you see today are direct descendants of the fiber glass bags that appeared in 1963. They have gone through a few styling and production changes, but are essentially the same.
You can look at an FL from the mid 1950's and see literally the very same styling today in the Road King Classics. The FL bikes changed very little over the years appearence wise, with the exception of hard bags and the Bat Wing.
With 1965 being the first year of the Electra Glide, you have the basis for all future incarations of the Electra Glide, I.E.; FLHS (sport) Road King, etc...
Take a look at your floor boards, the D shape florboard has been in use since 1966! The first year of the Shovelhead FL's used those, before that it was the Half Moons since 1940, with minor changes.
The Road Kings are versatile bikes, if you want retro, you can easily change the look to any era of the Glide style FL as a lot of Assc. parts are still being made. Take the Nostalgic Saddle bag guards, they first appeared in 1964. The nostalgic fender rails you can get for front or rear actually have been around since 1968. Although the same ones you can buy for a Softail are the same ones that were available on FL's prior to '68.
Hope this helps in the P&A department for looks...