Running a 6V DC LED Bulb from a 8V AC current source?
Your easiest wiring would be to do this:







simulate this circuit &ndash; Schematic created using CircuitLab

which gives full-wave lighting, but it'll be rather bright.   It can be adjusted by raising the R1 value.
White  LED forward voltages are about 3V, red around 1.2V, so the LED
color matters.   Except for some very bright lamps intended for
bicycles and lanterns, a "6V" LED is rather unusual (and probably expensive).
Flickering at 120 Hz is unlikely to be a problem, so a capacitor is not
necessary.