501 is a type of bulb (here in the UK anyway)
isnt tought to do i really should have done a write up so heres a quick one, just for you
(501 is a bulb btw!)
remove sidelights
cut them just on the other side of the line and i used a glue gun to reseal the holes so condensation doesnt seep in
sorce another pair of 501 bulb holders and fit amber 501 bulbs
piggy back the new holders onto the exsisting indicator bulb (because it uses a much bigger bulb and taking the bulb out of the loop will speed up the new 501 making it look stupid (and an MOT fail)i also sprayed the old bulb black and hid it out of the way (some people can take the thing out of the loop and wire in a resistor but i couldnt be bothered)
remove the old sidelight and relocate to the main beam lamp (full removal is needed as you will need to drill a hole in them to for the old sidelight but i hear you USDM guys have a hole for a sidelight in the main bulb unit?) i used a hot glue gun to hold them in place
repeat on the other side lol
put the car back together, took me an hour and a half in total