284/484 mopar cam for 340

The motor in the car was built by a company in Michigan before I bought the car. I have all the resets and the engine builders spec sheet on the motor and it says 10.5:1 but I don't know that to be the gospel truth...honestly who knows that all I have to go off of. So another question, if the car isn't 10.5:1 and it's actually lower what problems would I have with the motor and having lower compression?