I don't know what your using on the nh3 bar ,  but I don't know why the 370 won't pull it if it's currently being pulled with the 335 .  The 13.5 I believe will give more trouble than the 9L that being said  I had a 13.5 cam go bad at 8600 hrs and wasn't a cheep fix , if the 370 will work I think I would lean that way .