I have new headlights, all new turn signal l.e.d. indicator lights front and back. Headlights turn on but passenger side are extremely dim on both settings low and hi beams. Turn signals don't work at all, rear passenger side lights stays on, front signal lights are also very dim. This for a 62 impala.
I'd also be curious as to what kind of volts you're getting at the headlight versus what they are designed to work with? 50 yr old wiring isn't doing you any favors, and if you're running a stock alternator, they don't output well below 2000rpm (ish).
Might be some corrosion on those headlight plugs and/or the wiring. An Ohm-meter could also be used to see how much resistance you've got.
If you have a dedicated flasher for LED my suspicion then falls upon a 56 year old white nylon plastic turn signal cancel cam. White nylon was the second man made plastic invented. It turns yellow and brittle with age. My guess is that yours is broke (a technical term).