not exactly, i don't think so. The Newark Street M-85 should be the same dimensions as the classic "chambered" 1969-1970 M-85 (the deep/fat one)...2.75 inches.
However, there is also a New Hartford *fully hollow* GSR M-85 bass that is 3/4-inch thinner (skinnyer) in the body, than the Newark Street or classic/vintage chambered M-85. (still 1/4 inch deeper than the 1970's solid skinny M-85 though). I do own one of the 25 New Hartford GSR M-85's, and it is truly amazing. I like it better than the deeper M-85 on several levels, for my personal preferences (ergonomics, weight, resonance). I have held/played Grots 1970 deep chambered M-85, but never held a Newark Street M-85. I did play a Newark Street SF bass, and also own a couple vintage SF basses. It should be noted that both Newark Street M-85, and the New Hartford GSR M-85s, were advertised with spruce tops, but I do not think either one was actually made with a spruce top. the GSR has a mahogany top, and the Newark St probably has a maple top. here are the original specs, pre-production--
http://www.notreble.com/buzz/2014/01/19/guild-unveils-new-m-85-bass-models/
again, it appears they did not stick to that. the top of the GSR is definetly mahogany, not spruce.
To answer the original question of this thread, no, you do not need both a Newark Street Starfire bass, and a Newark Street M-85 bass. unless you were into collecting the different Newark Street models...that of course is another story, and in that case, both would be mandatoty.
most would prefer the thinner bodied, semi-hollow, Starfire bass, with the larger surface area on the body of the instrument and the f-holes.
some would prefer the deeper-bodied, chambered, M-85 bass, with a much smaller surface area on the body of the instrument, and no f-holes.
if they mass (lack of a better term) produced the GSR M-85 that I have, fully hollow, 2-inch depth, in mahogony...it might be more of a toss up, but i'd still lean heavilly towards the Starfire bass, as more than anything, they are different beasts altogether. And the SF just kinda is what it is. but everyone is different