ive installed a couple of fmic in my time. First of, is it a kit ie just jap kit or the likes? I found that with these "bolt on" kits, it actually required alot more work than simply bolting it on.
With the horns, you should have alot of room where the horns are located if its slightly pushing against the cooler then simply push it towards you. Best to post some pics up to get a better understanding of the problems your facing.