OK some basic info... as you've discovered not all flashers are the same, there's a bunch of pin assignments that exist, and there's even 2 and 4 pin flasher units. You have to get the right one for the vehicle it's going into. The pins should be numbered, make sure you have the same numbers on the same pin positions.
Standard flasher units will flash fast if you replace globes with LEDs, but will flash at the normal rate it you simply add LEDs but leave the globes in place. This is because LEDs use less current than globes so the standard flasher thinks you have a blown globe. You can use load equalisers but they're messy and inefficient. The correct solution is a dedicated LED flasher.
LEDs (as was pointed out) have polarity, positive and negative must be connected the wrong way or they won't work (and can possibly blow, however it's unlikely).
If you replace all your turn signal globes with LEDs you'll run into a problem with the turn signal globe in the console, as it's actually a connection between left and right.The easy fix is to simply remove the globe - the right fix is to add two small, cheap components (diodes) and a 3rd wire connected to a negative source (eg: the negative wire running to your tacho/clock).
