I'm swapping my 963b loader's engine with a engine out of a bus,can I use the damper that on bus motor it's like 12" and the one loader's engine is 9+"which there is room for the larger one
Pick through the builds for both serial numbers. Obviously, there will be a tremendous number of different parts. Pump settings, possibly camshaft, injectors, compression ratio, and on and on. I'd be leary of just swapping a balancer, especially not knowing if the rest of the package is different. And, I'm certain that there are more than just a few differences.
If you want some comparisons made of the differences between the two engines start by posting the Serial and Arrangement Numbers of both.