A long-rod motor is what you´ve got if you´ve got a ´71 Bonneville (or Tiger/TR6). The rods in question are the connecting rods that connect yer pistons to the crank. If there´s a long-rod motor, there must be a short-rod, yes? Yes! The T140 750 Bonneville (strating in ´73) does indeed have shorter rods, and a 5-speed, which brings us to yer next question. Yes, the 5-speed will fit yer ´71 T120, but a little machining will be required. If you are interested in the 5-speed purely cuz you want an extra highway cruzin gear, a bigger rear sprocket would be a cheaper and simpler solution. Okloveyoubyebye! -Chachi