I am about to install gauges and I have a question about where to get the reading from.

I noticed that there is a 1/2 or 3/4 NPT plug on the intake next to a sensor. Would it be ok to pull the plug there and using a reducer get the boost reading at this point

 

I used a port in the intake, but IIRC it was 1/4 or 1/8.

 

You can either drill your air horn 5/16 and use a 1/8 NPT tape or just buy the boost bolt from Geno's Garage for a couple bucks that just replaces an existing intake manifold bolt.