I have my heart set on a 5.5" Super Blackhawk but I noticed it comes only with the fluted cylinder. Aesthetically I like both for different reasons. However my concern is with the strength. I was curious if the flutes were originally left out for the sake recoil reducing weight, strength to the cylinder walls, or perhaps both? I have three boxes of the 340 grain +P+ Buffalo Bore that I would like to shoot and will probably buy more as well. Is this something that I should worry about? I'm guessing I'm overthinking this and I should be good to go.

I have one of those 5.5 fluted cylinder super blackhawks. Really nice revolver.
Why do you want to shoot such s heavy load? I'm not sure anyone should recommend what is safe for you to shoot other than the person liable.

Ask buffalo bore.

The weak spot of a cylinder on a 6 shot Ruger single action revolver is the bolt notch which is the closest part to the chamber fluted or non fluted.
If you want to get wild get a 5 shot cylinder they are much beefier.

http://www.customsixguns.com/writings/dissolving_the_myth.htm

You're over thinking it man. Pick the barrel length you want and whatever cylinder comes with it, be it fluted or unfluted, will handle most anything you can load it with. You will not be disappointed.

Curious though: What are you shooting at with 340gr Buffalo Bore?

Bill Ruger designed the original Super Blackhawk as an homage to the Colt Walker Dragoon, which was the most powerful handgun available in the 1860-70s.  It was style, pure and simple.

Before you shoot those 340 grain Buffalo Bore cartridges, be sure to get a referral from your primary care physician to a hand surgeon and neurologist.

However, if you really plan to use the gun for such heavy loads, strongly consider the Bisley frame variation, as that handles severe recoil much better than the plow handle grip frame.

I went salmon fishing in Alaska last year and then caribou hunting in Alaska this year so I figured I would get something that would work well on bear and human in the event either wanted something that I had bad enough to fight for it.  

For those loads you need to be looking at a Bisley. The grip frame will handle recoil MUCH better.

The fluted va unfluted cylinder is simply personal preference.

the Ruger SuperBlackhawk is a very strong design.

I like 'em fluted.

I would wait before buying any more, you may be surprised how long those other 59 rounds will last after you touch off that first one.  Recoil with these loads, especially in a short barreled Ruger SBH, will be downright brutal.  Makes shooting them off the bench flat-out not fun, even with gloves and ear plugs under ear muffs.  I know years ago, I played around with some 300gr hardcast lead bullets over stout loads of H110 & 296.  I was shooting them in an indoor 25 yard range out of a 4 5/8" and 7.5" SBH, and the people shooting next to me packed their stuff and left.  I mean, they stopped half way through their range session, packed up everything, and left...concussion and blast was that bad.  I'm not sure if you have shot any truly heavy loads out of a short barreled revolver, but it isn't any fun.    

As far as the fluted vs unfluted goes, I'm an unfluted kind of guy...

Those are amazing, I opted for Ajax buffalo horn gunfighter grips on my Bisley conversion

Its a non issue the flutes lay between the chambers, most people who use the SBHs prefer the 5.5" guns as the weight diff is noticeable, and they balance well.
I still shoot a 1959 44 Blackhawk and have been shooting 320 grain cast over 21.5 grains of 296 for a very long time and this gun has never had an issue of any kind.
ETA for a very long time that 340 grain BB load was not approved by BB, this was not a gun strength issue, it was about cylinder length, with any crimp jump the gun was locked up. They must have sprang for a good crimping die.
If you are going to shoot strong loads in it you will probably want to put a Hogue rubber grip on it. A Free Spin Pawl runs about 30 bucks and takes just a few minutes to install this is a very nice convenience.

OMG can't wait to get the Bisley I ordered

Here is one of my unfluted hand cannons...




...Magnum Research BFF in .45 Colt +P+, with 5-shot cylinder.  Gun was sent off to Mag-na-Port for an action job, jeweling, and porting....but I am thinking about shortening the barrel to just forward of the ejector housing.