hey Mark,  can you use the vacuum  from the trucks engine  to  evac  the system???

That is a good question. I guess you could, but not sure how strong of a vacuum it will pull. 29.9" of mercury is a perfect vacuum. The low side gauge should read to 30", but without a micron gauge you will never know for sure. Not critical for this type of system.

I think you will only get 15" from the manifold.