I'd try a 4 hole 1/2 inch. If you want to go w/ a longer (/6) throttle cable and use a drop base you could try a 1" although not sure if it would help. I see they have new tapered 4 hole spacers I might try one of those on my 440 build...but they aren't cheap! Ine good thing about spacers is they get the carb off the hot intake. Make sure you get the valley pan w/ heat riser block offs. This will also keep the intake temp down. Good luck.