andair
I used the Andair gascolater from Vans on my 9A with o-320. Plenty flow. Andy told me at SNF last year that he designed this part for adequate flow to 180 HP. He reccomended the Big Boy for the 200 HP and 540 installations. That being said, it sure would'nt hurt to use the big one. Just remember it will have more hot surface area to heat up that fuel.
HTH
Chris