I believe that was what Sikorsky offered for what was eventually won by the Boeing 107 Sea Knight.I remember reading that a model of the S-61R/CH-3 was offered to the USMC at one time for transport ,but I assumed it looked just like its AF counterpart.
Iranian F-14A, I've been reading
Marines and Helicopters 1963-1973 by William R. Falls, in which he states that 'In 1958, Gen Randolph McCall Pate, Commandant of the USMC requested the Chief of Naval Operations to purchase modified Sikorsky HSS-2 [SH-3 Sea King] as replacement for the Marine's Sikorsky H-34, which Pate coined the "HR3S" (Helicopter Transport 3 Sikorsky
It was specifically specified that a rear ramp arrangement to be incorporated into this modification.'
From this book, it seems it was a combination of Naval allocation of budget (or more correctly lack of it), as well as Sikorsky having engineering problems with the transmission coping with the horse power which delayed the S-61R simply being selected and put into USMC service.
In the mean time, Vertol (Boeing Vertol?) was quick and clever enough to market it's privately funded, developed and most importantly flying 107A prototype to the USMC. Hence as a consequence, because of this flight demo of the Vertol 107A and the continued development of the S-61R, the US Navy elected to formulate the 'HRX' Competition [which I must add, I'd like to learn more about, but can't find anything on this forum pertaining to 'HRX']
Hence circumstances unfolded, the Vertol's 107A design became more attractive to the USN/USMC, clever marketing prevailed, next thing you know, a modified 107A became the CH-46A Sea Knight.....
P.S. I'm assuming the S-61R utilised the S-61's rotor systems, perhaps with the exception of the folding/stowage systems....So I'd assume that a ship-based ASW/Assault Transport derivative of the S-61R could simply use/revert back to the original S-61's folding/stowage rotor system arrangement...
Or did the later CH-3E that the USAF adopted, when the program was dropped by the USMC always retain a folding/stowage type rotor system due to the original USN/USMC requirements??
Regards
Pioneer