Mine loves the Carlson's Longbeard XR choke with Longbeard XR's #5s in the 2 1/8 oz (heavier of the loads they offer) in 3 1/2 inch.
That's just my gun, I've heard many guys' guns prefer the 2oz #6's if you're going the Longbeard route those might be two places to start.
Definitely other options to consider, but for my gun I've found it's hard to beat the performance of the Longbeards for the price.