The SU HS6 carbs on my 66 122S had worn shafts for the throttle butterfly causing air leaks and a fellow in Mass had a business replacement shafts and boring the bodies with a rebushing them with it delrin reamed to size of the shafts. It was worth the investment and twin SUs were so much more fun, even with seasonal tuning the SUs required.
So, get the carb solid and it will make it run well and take a unknown curve out of the troubleshooting.
Leaky carbs can really make it hard to tune and run optimal.
Nothing you don't know.
A dual piston caliper could solve the braking challenges at the expense of period looks, or a pair of single piston calipers like off a honda might work.
Take a page from FunJimmy's approach with a twist....
he used a modern std fork with multiple pot caliper and single drilled disc. His approach was high $ but, twist the equation.
Source a decent pair of fork tubes that can provide damping you want, hopefully the trees are compatible. Otherwise it starts getting pricey too fast.
All balls replacement bearings for the different forks and trees. Then the axle and wheels that can look close enough.
Maybe your current forks are fine and just need replacement tubes to remove the chopper rake.
Then adapter for a good caliper picked up cheaply and rebuild it.
