skateboard assembly

Question
i have newly assembled a skateboard of mine,the deck size is "32.25X8.25" i want to replace it with another deck"7.5X31" because i want to play [street skateboarding" not "transition type" the problem is that i am confused between buying a new deck only or should i buy a complete skateboard.the reason for the confusion is that my current skateboard has a really weak ability of turning and i dont know if the reason of this is the deck or the truck. note :my wheels are 50millimeter.
thanks ,hashem

Answer
Assuming you've tried loosening your trucks by loosening your king pin (the bolt that faces down), having a skinnier deck probably won't help in the turning department.  The type of trucks usually influence your turning, as well as having riser pads to avoid wheel bite (when your wheels touch the bottom of your board due to loose trucks).  See if you can try out a friends deck that has different trucks.  I've always liked the way Independent trucks felt, and Gullwings back in the day.  Trackers were okay.  I've had Thunders and Venture's but went back to Indy's and have stayed with them for the past 8 years.  Try a few of them if you can.  The deck will only make a mental difference, however the trucks will make a noticeable difference in turning since they are the major component in that equation.  Wheel size will also make a difference, but more in responsiveness, not in overall ability.