Picked up a slant for the first time

Welcome to the forum, looks like you got a good one there.
As for the super 6 manifold, make sure you get all of the parts it came with such as carb, brackets, and air cleaner.
I also would suggest that you upgrade the exhaust to a bigger pipe from the manifold back, the original is smaller than the outlet and chokes the flow a lot.
The gears are a good idea as well.
Good luck, and keep us informed on the progress........