Well, when you say, "my cages and straps scrape against the ground," do you mean that you're putting your foot on the underside of the pedal so that the cages and straps are hanging down below the pedal as you ride?
If so, you're doing it wrong and you should either remove the cages and straps or flip the pedal over and put your foot into it correctly.
Other than that, the "standard" length for track cranks is 165mm and the size of the chainring will depend on the size of the cog, so you should use a gear chart to figure out the proper gear ratio for you and get a chainring/cog combo to achieve that ratio, and, since your frame is Japanese, why not go with Japanese components, too, and get Dura-Ace track stuff if you can afford it?
Good luck, and the link below is to a gear chart webpage...
