Should I Change my Bit?

Okay here is another one........I have a 5yr old thoroughbred gelding who was raced and Im currently ridding him western and when I put his bridle on he stretches his neck out and chomps on the bit but takes the bit very well, the bit that Im using is a Tom Thumb Argentine Training Bit should I change? I thought about buying the same bit that was used when he raced, but someone told me that I wouldnt be able to stop/turn him. What should I do?