blanked up turn signal, PLEASE HELP ME

[70CHEVYBB]

I turn on my left turn signal and here's what happens----- dash lights flash, tail lights, grill lights, and all side marker lights flash. I have driven the truck for a week with no problems, I installed a ground from the rear cross brace to the frame and that's when I noticed it started screwing up. I removed the ground and didn't help. I have all new bulbs and have the following grounds, battery to radiator support, battery to block, block to frame, side marker lights to radiator support in front, side marker lights to bed in rear. Both head lights to radiator support. All grounds were attached to bare metal. The right turn signal works perfect. any help would be great cause I can't drive it til I get it fixed.