im buying an crate motor 383 stroker and wich is better one or two peace. i know about the diffent flex plate's and balncers's need for ether one or two peace.

what stall of conveter for 405hp 440tq 383 i figgerd 2300 to 2500 stall.its cam is 234 intake and 244 exsawed @.050"  

one piece usually doesnt have as many leak problems  

Depends on how hard you're gonna turn the motor. In high rpm situations, the one-piece seals have a bad tendency to blow out.

For a street application it should be alright.  

Forgot to metion, on the converter, what rear gear are you running? You need to determine that first before picking a torque converter.