The coil on an A-body turn signal flasher unit is in series with the load

Yeh........LOL and it's why they don't work well with LED's. "Back in the day" (expensive) Trucklite used to sell plastic cased ones you could see into. They were solid state with a relay and "claimed" they would "flash anything." But since they were for trucks, I imagine the claim leaned towards MORE load, and not less

Same idea, Signal Stat, "used to be" another great brand

Genuine-New-Signal-Stat-Flasher-172-Heavy-Duty-12V.jpg

I may be mistaken, I may have been thinking of Grote