I figure you would need more gearing with a torque converter. top speed sometimes is not good to have on some trail riding. it more about trying to accelerate as fast as you can to the next corner.
how bad is the wheeling for you? can you hold it initially when taking off? does it want to wheeling on you coming out of a corner from low speeds?
you may have to compromise on how much gearing you can put into the
bike if the wheeling is uncontrollable?
I have found also sometimes if you feel the handle bars are to close to you? you can off set the handle bar mount forward couple different ways. for example with a different set of clamps that have a off set to them.
also if you thought your handle bars where to high,which they are probably not. you could go just little lower.
what will happen with theses small adjustments it will allow you body weight to go forward little more and keep the front end down. also doesn't help having the motor in the middle of the chassis....