Ray,
I'd say there's very little difference between the butterfly shafts at 2000 rpm, such that the difference between the butterflies at idle is not noticable. The idle can be adjusted with the slow run screws.
The setup - except for the vacuum ports - does no permanent change to the car - so you could relatively easily change it back to stock.
Edit: I've threaded the lower half of the vacuum port holes to accept SU cheese head screws, which can be installed in place of the brass ports for a stock look.
The female adjuster, with the screw and coil springs, is pinned to the front carb using the stock pin setup (#32 drill). The rear carb male adjuster is pinned to a 5/16" D shaft which rotates within the female adjuster bushing. HD6 "W" clamp joins the cross shaft to the rear carb.
Suggest this: loosen the W clamp, use the fast idle screws and gauges to raise the rpms and get roughly equal vacuum. With the W clamp still loose, center the Weber adjuster. Tighten the W clamp, loosen the fast idle screws, then use the weber adjuster for the final equalizing on the gauges.
I didn't use the fast idle screws at all, but merely held the throttle open by hand while adjusting the weber screw. The point is you can't do it all with the weber adjuster. You have to get it in the ballpark first, then do the final adjustment with the weber.
Use of the HD6 "W" connector allows easy shaft removal without removing either carb.
I used these bushings (Amazon). They have an accurate ID which allows movement with little slop.
Weber balancer parts available on eBay. Some reshaping of the periphery required. I also cut down the male tang. Used vinegar to dissolve off the yellow zinc chromate. In future will replate with clear blue zinc. I used a step drill to drill out the oblong weber holes to fit the bushing OD. Silver brazed the weber adjusters to bushings.
5 mm vacuum ports. I plugged them with 4-40 Allen screws under the rubber caps.
EDIT: For stock BJ8 setup suggest drill & tap the insulator blocks rather than the carbs.