Is this the intake manifold vacuum?

Thanks Brown and Krazy--one last question--so I've been reading up on the vacuum fitting since I need to obtain one that has the large fitting coming out the top. Some of the material I came across indicated that I may not have enough vacuum to run the big port out of that tree which has the other hoses already connected. It mentions other intake ports that could be used as a dedicated line to the power booster, but I think my other inlet is being used to support the AC unit. (can see in the pic) Does anyone think this is wrong and I should be able to just plumb it into the big port of the new tree? Again, it's stock 318 with standard cam.