Theoretically yes. However, cylinders are factory fitted items. Sometimes they will just drop in and fit great, timing and b/c gap both. Mostly, they won't.
Mr. Jones where are you located at, I have a six shot cylinder that I will trade for the 7 shot, and if you are close at hand I will fit it for you. I'm in Morgantown WV right now.
I had a 7 shot 686+ converted to 6 shot by S&W. I now have both 6- and 7- chamber cylinders, each with it's own extractor rod. The cylinders are interchangable - I can swap them anytime just backing out the crane screw. According to S&W gunsmith the cylinder is the only difference between 686 and 686+; the hand and all other action parts are same.
Name of S&W gunsmith who did the job for me is John Seyfert. If you want to have this done, ask to get John on the phone. Customer Support rep had no idea what I was talking about and sounded a bit scared.