Vacuum Source

If it's even size 1/4 or 3/8 use ratchet components. If it's odd size like 5/16, you'll have to go to the hardware store and get a 'chunk' of square keystock. Frankly it matters little whether the PVC is "off the carb" or "off the manifold" so long as they both "are." That manifold fitting, as well as the one "in one runner" of factory intakes MAY cause a bit of fuel distro problems