Check here: https://www.carbkitsource.com/Rochester.html You will also find other options by simply doing a Google search. I've never used this place, it is just one that popped up.
Buy it from Greg Gessler, here is the kit you need with ethanol resistant parts, https://quadrajetparts.com/rochester-carburetor-rebuild-buick-1970-jeep-p-448.html
I would think going up a jet size or 2 would help with performance if you have added dual exhaust from single and the ethanol runs leaner also. Add a few degrees of timing also. Should improve mpg
Let me do that for you since you just fell off the Mellon truck. https://www.google.com/search?q=Car...rome..69i57.2518j0j8&sourceid=chrome&ie=UTF-8
