The Constitution Class Heavy Cruiser is a design by Matt Jefferies. The "Phase II" variant is the interum design, between TOS, and TMP. Orignially intended for the comeback of the series. It was redesigned again, as it was desided to go with a movie.
There are a few differing variants of the "Phase II", as even the original schematics aren't the clearest. This is my take. Though I seem to be the only one to stick with the red lighted Bussard collectors.