Pulling a little bit locally its a stock tractor pull with a transfer sled. I have a c-120 with a K-341 (16hp) when pulling it spins out in 2nd and 3rd it looses power. What i'm wondering how big of engine pulley can i go on the engine and still use the stock belt gaurd as i could use a little more speed also running 23x8.50x12 ag tires.