Steven: The crank arm can be drilled out and tapped for a threaded insert called a Helicoil, which will restore your threads. Check with your local bike shops or less likely, a machine shop. You will need to end up with a 9/16x20 left-hand thread. You could also buy a replacement left crank arm. I wouldn't recommend epoxying the new pedal into the stripped crank.

Whatever approach you take, be sure to grease the threads of the new pedals before you mount them to prevent seizing of the dissimilar metals. I recommend Tef-Gel. Stainless steel pedal washers may also help get them loose when the time comes.

Use a proper pedal wrench when you mount the new pedals and torque them well, loose pedals are the leading cause of stripped crank threads. It sounds as if you were able to exert plenty of force with the tool you used, though.