My WP pulley was 7" and I replaced it with a 6.33" diameter, That allowed extra belt clearance. The flow might increase slightly but I have noted no difference. Additionally my main crank had a dual pulley but the rear grove did not align with anything, so i installed a bolt on third pulley that bolts to the face of the original crank
This is how close my wp pulley was to crank, pictures here
http://67-72chevytrucks.com/vboard/s....php?p=7958499
I can get some pics for you when i get home if you'd like