Why don't you just pull the 340 and get crackin' on it and use whatever $ and energy that you would spend on acquiring/rebuilding something else into it?
11:1 compression, solid roller, light weight rotating assembly to a 4 speed. Its exactly opposite of what i want now. It's an amazing motor but i just went over the top on the build. It's like driving with an on-off switch. Either im bogging it trying to take off smooth or i'm sideways through the intersection.