There are no commercial tank blocks available that use the threads on a QB tube (or 22XX for that matter).... You can use the factory QB79 block, or a duplicate made by JDS Airman (which has better mounting holes, but no center pin to open the pin valve in a regulator).... either require a full thickness tube (ie you have to remove the threaded portion) that must be drilled accurately so that the QB79 style block will mount safely....

There is no reason my "reversed style" tank block that mounts to a QB (or with a different adapter to a 22XX) tube could not be made "forward facing" instead of reversed, and of course the depth could be made so that a standard 9 oz. CO2 tank would fit (they are currently about 1/16" too large to fit a QB79 tank block), or even deep enough that a regulator with gauge and fill fitting attached could rotate under the barrel.... All it takes is a machinist to produce them....

Bob