Originally Posted by Landgolier
You just need bmx cranks. Totally easy to do. I wouldn't go calling it a "track" bike though, as everyone who is making fun of you for calling a chainwheel a crank will get all uppity again, but as the links show this is totally doable. What I can't remember is what the standard BMX chainline is, so you might have annoying chainline issues.
But BMX one-piece cranks require a different (larger) bottom bracket shell than you find on most road/track bikes. Those links are to bikes with a bb shell made for a one-piece crank. I know there's some hardware you can get to convert a one-piece bottom bracket for three-piece use, but is there a way to go the other way?