[Christ]

Put it back together, so you don't lose any parts. IF another opportunity comes up, you can always pull it back apart, and this time, you already know how.

If you want to experiment with gearing, you could always have some straight gears milled, which would increase noise, but at least they'd give you an idea of your optimal ratios.

Not that I'd recommend it, but you could actually mill short-term use gears by hand (with a lathe and files). I say short term use, because you don't have the proper equipment to harden them and such... you'd be using them for a tank at most, and then you'd have to take them out for inspection, which may be more work than you want to get into.