Apparently the dial gauge extension housing has a second extension that, when assembled together provides enough length to attach a dial gauge forward of the vacuum pump. Otherwise, you will need to remove the vacuum pump.
The belt tension pin wrench: Does your engine have a belt tensioner?
Additional tools you will need:
Dial indicator
Camshaft pulley lever (shown
here)
Additional tools that make for a much better experience:
Dogleg wrench (for tight space rear camshaft pulley bolt)(also shown
here)
Others are encouraged to list their favorite versions. Some have found suitable on ebay.