You can find 6V LED tail light bulbs
http://www.superbrightleds.com/cgi-b...57-x12-24V.htm
I run these on two cars. You want the white or clear light not red. Note this is for an 1154 type bulb socket (offset pins in the base ) so make sure your sockets are for this style ( NOT 1158) or you will have to change the socket .