All you need is one of the "electronic" flashers. The ones I've seen are all plastic (see through) housings.
Front signals may not work, depending on how they are wired. I think they are called non-specific polarity LED's (or something like that) (and maybe the fronts too, since they are lights + flashing) that will work around that problem, but I haven't delved into it that far. Problem with a "normal" LED bulb assembly is that they only work with voltage "one way" (IE + to + and - to -). Any of the lights that serve dual purpose (flash and light) and are single filament the polarity actually reverses to make them flash, which means a normal LED will either work as a flasher, or as a light, but not both.
The rears are easy. Buy 1157's off of ebay. Make sure the LED color matches lens color (IE red leds for red lenses, amber for amber, etc) but I have yet to find an LED bulb that works anywhere near as good as incandescent for reverse.
You want SMD's (not the oval headed LEDs). 5050 SMD's are brighter than lower numbers. Make sure they have LED's radially along with facing straight rearward, and the more LED's you have, the better. Make sure the bulb isn't longer than what will clear the housing. That is a problem with the side markers (194/168's) for certain. Brake lights have quite a bit of clearance as I recall.
