well providing you haven't got the leads switched at the lights so your weaker element which normally is the parking light versus the brighter one which should be your signal element is the one doing the flashing- you may already have a heavy duty flasher.if I understand it right you only need a heavy duty if you are using extra lights from a trailer or add on lights somewhere that pull extra load. otherwise the current going through the flasher may not be enough to make it function fast when you are just using the regular pickup lights.
