I' ve heard good things about Kicks chokes. I use the one that came with my gun,extra full. You definately need a full or extra full.

Shot size, only one way to determine that. Buya few different sizes and shoot the gun. There are a few sites where you can down load Turkey targets for free.

I like N0. 4' s other people swear by 5 and 6' s. Just find out what works best, brand and shot size for that particular gun. Federal and Wichester in the same length and shot size shoot differently in my gun.