For motors, just a drop in:http://m.ebay.ca/itm/251757448977?_mwBanner=1 they are about 3$ apiece, and can run anything from stock aa's for "stockish" performance, or I've personally run them on 3 trustfires with no issue. I would however upgrade the rev switch to this puppy:http://www.allelectronics.com/make-a-store/item/sms-310/15a-spdt-snap-action-switch-w/lever/1.html, simply shave down where the stock switch sat and screw this into the post where the cover screwed into with a slightly longer screw.
Just to be clear, do you consider "koosh" darts as elite style darts? I simply would rather not drive two and a half hours to get there, and then find out I have the incorrect ammo.