sounds to me like you already have a ton of low end power. long rod wont increae power, it will simply increase reliability. 4mm crank will give you more power but youll have to redo the porting in your cylinders to make it work right. i persononally highly recommend eric gorr's woods port. itrs got awesome low end and midrange power. i dont know about the porting you have but by "full port" i think of top end...