Sounds like you stripped the heads, not the threads. Drill out or grind the bolt heads down so you can remove the primary. There should be enough left to get some vise grips on the ends of those bolts and back them out.
Maybe you were using the wrong size torx bit or it was not the best quality.

 

I went through this also. I (a buddy) was able to get 1 out using an extraction kit (https://frontporch.club/galleries/br...craftsman.html) and then the other two were reversed out using a chisel and hammer. Good luck.

 

 

Drill the center and try an ez out..... I've had a lot of success with those.
Steve

 

 

I've had this happen on old neglected Sportsters. Drilled the heads off with a 1/4" drill bit, removed the derby cover and grab whats left with vise grips, they come out pretty easy when there is no tension on them.

 

Maybe some "Liquid`Wrench" on the heads/threads. Be sure to tap the heads with a brass hammer.