If the convertion means the calipers dont seat on the car at the same angle as they did on the car there are off they may still be air in them.

You need to make sure the bleed nipple is at the highest point when bleeding them, may have to unbolt them from there mounts just to bleed them and put them back on to test the pedel (I had the same prob on a kit car a while ago took me a while to figure it out.)