There were no alignment issues with the belt but as I was going to use two belts to spin the alternator was necessary to add a double sheave which I also bought from American Diesel. The original belt stayed in place to turn the water pump and old generator which served as an idler but can also be switched to be brought on line if the larger alternator fails.
The new alternator mount replaces the OEM mount on the block and required a shim, actually a machined block, to fit to the flexible mount. Works very well.
At 200amps your alternator is probably a large case. You will need a alternator bracket to fit which will bolt onto the new mount. If alignment adjustment is needed, it can be done there. Good luck.