On a '65 nickel SAA the grips/stocks would have been 2 piece walnut, or the black hard rubber grips, which were the standard grip/stocks on the blue/CCH SAAs. Colt changed to the black plastic eagle grips in 1968. The hard rubber grips used pre-1968, were not left over 1st gen grips, but were new production; there are a couple of 2nd gen variations of the hard rubber grips with and without a Colt Hartford address and slightly different pattern on the interior of the grips. The exterior of late 1st gen and pre-68 2nd gen grips are virtually indistinguishable, but the inside pattern and/or the Colt Hartford address tells the tail.
It is highly unlikely that the grips on your gun are the reworked originals. Someone would have had to totally re-contoured and reshaped them as well as converting to one piece. The walnut grips/stocks used on nickel SAA are not fit flush to the frame as those are.
Best regards,