You could try the taps, the size is 9/16" X 20TPI, right hand thread for the right crank, left hand thread for the left one. You could also try starting the pedals in from the inside and seeing if you can re-form the distorted threads enough to thread them in the right way. Understand that a tap can only remove metal so if the fit is too loose due to the metal being stripped out there will be nothing to tap into. In this case the repair is to drill the hole oversize and using a special tap make new, oversize threads and then install a Helicoil threaded insert. This will make stronger threads than the original aluminum. An older bike shop or a machine shop would be places to inquire about this. It is a quick and relatively simple job but the cost of the specialized tooling (taps and insertion tool) required makes it uneconomical to do yourself.
Grease the pedal threads and start them by hand so that you do not damage the threads again; if they do not go smoothly STOP and find out why. I use Tef-Gel anti-seize paste and also stainless pedal washers to help prevent the pedals binding or galling and to ease removal.