62 C10 LED Light issues

[Bonello711]

Recently purchase an awesome 62 Chevy C10... Everything worked fine (turn/flash/brake) until I installed new LED front and rear turn/brake lights. It already had the aftermarket turn signal switch and it's a 12 volt system.

After installing the LED's (type that just plug into the bulb socket), when I turn on the left signal both fronts light up bright and stay on without blinking and the rear left lights up very dim (nothing flashes) and the right is basically the same (both fronts light up bright without flashing and the right rear is very dim).

I put one of the old bulbs back in and it started flashing but I'd rather keep the new LED lights. I am clueless when it comes to wiring and need help. Any ideas would be great, thanks!