When I was porting my motor it came down to two builders really, K&T and Passion. At the time Passion was still growing from a small company to what they are now- I chose Passion over K&T for several reasons.
Jim at PRE talked to me about my motor, set-up, chassis, track, tuning capabilities, etc etc. He wanted to know it all before he started grinding away at my cyls- I found that much more comforting than someone saying "send me your cyls and x amount of money and i'll send em back ported." I personally think its important for builder/buyer communications- everyone knows what is goin on with the motor.
Drag motors arent cheap, just remember you get what u pay for, but u can pay to much for to little.