Here's a set of gauges I use for sync'ing. They're an easy to read 2.5" dial with 1/2"Hg markings on the dial so matching cyls is no problem. I just mounted them both on a scrap piece of wood and made my own dampener to reduce needle fluctuation. The below photo's show some detail of the pulsation dampener but I just took a couple of pieces of scrap metal and arranged them so each vac line can be crimped as needed with a wing-nut for fine adjustment.

These are supposedly accurate gauges but as you know it's not the actual reading that's important. The equal reading is what we want here. To check that both guages read the same I hooked both lines to a 'T' fitting and pulled a vacuum with a brake bleeder. Both guages read EXACTLY the same to a small fraction of 1"Hg (much less than the needle width).

These guages are only about $15 each but very well made. There is even a manual bleed valve built into the top of each guage to equalize the mechanisms for barometric pressure changes.
With a couple of fittings from the hardware store it was ready to go.

I used Wika #38500 30-0" Vacuum Guages
http://www.gaugestore.com/prodinfo.asp?number=38500





Here's the detail of the hose crimp, without some way to restrict the line the guages will pulsate to much to make any accurate use of the readings.




I also made up a tool to easily get to the sync adjustment screw. Rather simple but it is very easy to adjust now, it's simply a 7mm 1/4" socket that's epoxied to some twisted brazing rod (coat hanger will do just as well). It can be bent as needed to easily catch the adjusting screw in 2 seconds with the engine running.