I used the same process on the MC as I did on my '64 Valiant and '37 Pontiac.
On those two I bought 1157 bulbs from superbright LEDs, and used the same flashers from Amazon, CEC 2 prong with a ground wire.
On the MC I used the same flashers but bought 1157's from Amazon.
Looking at the Superbright products, the have a slightly higher wattage draw than the Amazons.
I did add an additional 4 ga, ground strap to the frame,and one to the firewall. No change.
But..........with my head under the dash listening to the flashers click in both hazard and turn modes I pulled the lights on and the flasher started "stuttering", like they weren't latching, or like a starter solenoid when the battery is low.
Hmmm, not enough draw? I'm going to tap in an incandescent bulb to each side tomorrow and see if that helps.
I'll have to look under the dash to see where the harness is grounded and clean that connection. Any clue as to that location?
Another thought. I havent looked, but does the firewall bulkhead connection unplug? Maybe that needs to be cleaned.........