Ron,
Before you spend money on vacuum gauges, you might consider checking out my writeup on making a low-cost differential manometer (vacuum gauge). You can use a $3 section of tubing, some transmission fluid, tape, and a stick to build an assembly that will help you to synchronize two carbs. You synch two at a time, for instance 1-2, then 2-3, then 3-4, then 1-4 (just to be sure that error didn't get carried through).
It's easy, cheap, and surprisingly very accurate (it'll show a difference in very tiny adjustments quite easily). The only disadvantage as I see it is that you can't have it connected to four carbs at once, but if you don't mind going two at a time it's much cheaper than a gauge set.
Anywho, that's enough off-topic rambling from me. If you're interested, check out Community->Filebase->Non model-specific and search for "manometer" (or just browse for it -- the title is "differential manometer". Please feel free to contact me if you have any questions or concerns or just any feedback you have about the writeup.