You should not need to adjust the Idle Mixture. You will probably have to adjust the Idle Stops - but just a little bit.
The mechanical sync on mine were pretty close right out of the box using Vans install instructions. It was only when I did the Pneumatic sync that I could see that an adjustment was required.
I had one 30 year A&P said he didn't need gauges to set a carb sync and he could do it by ear. He was 6" of vacuum off. Use the gauges.
Now that's funny! Reminds me of a mechanic I used to work with about 40 years ago that said he did not need to use a dwell meter to set breaker points, he set them by ear.