My first thought is to find out if there's a problem before you go look for one. If your pump delivers fuel and the carb needle and seat hold the pressure, you might not need to worry about the pressure being too high.
If you are committed to measuring, though, my thought is to identify your carb inlet or pump outlet fitting and get creative to add a "tee" using rubber fuel line and barbed fittings.
Here's just one example:
Link to One Example Online
It might even be easier to do this at the fuel pump.
The hard fuel line will move enough to let you do this, whether at the fuel pump or at the carb.
When I chased a flooding issue, I went through this with a couple pumps so hang on to your test rig... you may need it again.
Mike