396/402 Engine Vacuum Reading

Hey guys...I recently got a 72 SS 396/402 and my father-in-law and I have been working on the engine. It's a numbers matching car, but someone did a poor tune-up on it sometime before we got it. The question I have for you is---

Does anyone know what kind of vacuum reading we should get on the car in park at idle (700rpm)? It's an air injector reactor engine, if that makes any difference.

I know this is kind of a specific question, and my knowledge of engines is layman at best, but my father-in-law is very good, and he's having a tough time getting this thing tuned...

Any feedback would help immensely, and if I need to provide more info than I did here, let me know...

Thanks again everyone for all of your help...It means a lot to a newbie owner..

John