I have a 67 Camaro RS and Im having a problem with my turn signal. Left one works OK. Right one flashes but when I step on the brake it stops flashing and stays lit and the left brake lights go out. As soon as I let go of the brake pedal it starts flashing again. Replaced the bulbs and checked both flashers and they work. Both Hazard and Turn signal flashers installed are 552's. Hazard lights work ok.

Reads like brake light power has been bypassed around the turn signal switch.

Normally, turn signals overrule brake lights. Check wiring at column, Dark green for rear brake up to fusebox, across fuse to a gray wire to column. Or could be turn signal switch itself, they do wear out, jiggle the handle.