there is nothing wrong with turning vintage bikes into fixed wheels. Touring bikes make a great choice for conversion if you want to ride fixed for distance. They have a more relaxed geometry and clearance for wider tires, allowing for a slower, but more comfortable ride.

Then again, if this doesn't appeal to you, sell it and buy something a little more aggressive.

and in the off chance the bike it french threaded, your LBS is full of ****,