How do you post a question in the forum? Every rock I bring is the wrong rock. Some help please.

I have a 1949 Chevrolet ½ ton with the original 216 engine that has been modified with dual Carter W-1 carbs and an electric ignition. I am the third owner on the truck after the first owner was a rancher that bought the truck new and sold it to my grandfather in 1955. I inherited the truck in 1972 and drove it original until 2000 when I tore it down to the frame and began a long restoration. The restoration is finally just about finished.
I just brought a 1949 Chevy 216 to life after twenty odd years. The 216 runs well and idles at 450 RPM. The concern I’m having is that the vacuum at idle is 10 inches vs the 20 inches I expected. I put dual Carter W-1 carbs on it. Do you expect the vacuum to drop when you double the carbs?
The compression on all the cylinders are good at around 115 PSI and the timing is on the mark. What do you think?