I just got my 65 chevelle led's for the rear lights and exon front headlights, had them wired about 6 months ago, didnt have a problem upuntil today.I pulled the head lamp switch and I seen them come on for a split second, then they seemed to have shorten out all the gauge lights could it be that thiers a bad ground or the switch is bad?

Xeon headlights will draw more power. If its the original wiring, it could have oveheated and failed. There is a fusible link near the horn relay but that would have killed almost everything. Ideally you should have realys and heavy gauge wires for headlight upgrades. I have a 67 with quad setup that I have some Bosch relays to do just this. The stock wiring had all the current draw for the headlight go through the switch...

Without more details on how it was wired... this is the what I can think of off the top of my head... Try posting more details on how you wired it up or if you had it done, go back to the shop...