I have an old Shogun frame that I'm converting to a fixie. It has an old Tourney ST crank on a square taper BB.

I have a Shimano Ultegra triple with BB that I would like to use, but I'm not sure if it will work with a single chainring. I plan on picking up a flip/flop wheel. Thoughts?

shouldn't be a problem. i have a 105 triple set up with a single chainring in the middle position and the chainline turns out to be just fine.

cool
Do I need to do anything funky with the chainring bolts, or can I just reuse the same ones without the big ring?

they'll be loose. you'll want the "shallower" track bolts.

They won't be loose if you torque them down carefully, but it's a pain in the ass to do that. Just get track/bmx bolts, but if you can't find them use what you got.

if you use the original bolts from the triple with a single chainring, chances are you won't be able to torque them down. so either get shorter chainring bolts or get spacers to use with the originals.

no, they'll be loose. there's no practical way around this-- he'll need single ring bolts.

Thanks y'all.

is this the same issue when converting a Campagnolo Mirage triple crankset? and if i swing over to Trackstar or a similar place in the city, will they have the right crank bolts for me?

bolts meant to hold two rings to the crank arms will be slightly longer than track bolts, which are meant to hold a single ring to the crank arms.
there could be exceptions to this (thinner spider, thinner rings), but in my experience, every double/triple i've converted required shorter bolts.

yes, they will have them. any shop (even big chains) will most likely have them. a shop specializing in tarck culture will undoubtedly carry different types, colors, materials, etc.