I'm still 6v and I don't care for the LEDs on an older vehicle so my solution was to replace the lenses with the new plastic type and upgrade the brackets inside my tail lights to take 21cp bulbs. They are significantly brighter than the stock 6cp bulbs and the plastic lenses allow much more light to pass thru. The combo also seems to illuminate the entire tail light lens rather than create a small hot spot.
Here's a pic comparing the lenses...plastic is mounted to the bracket and the glass one is hanging below.
https://farm7.staticflickr.com/6051/6321986157_bc78b90429_z.jpgPic of the plastic lens and 21cp brake light bulb illuminated.
https://farm8.staticflickr.com/7122/7657592246_24eec390ce_c.jpg
