Keep in mind that it's not just about paying the required wages but also about the record keeping. You can get into almost as much trouble for missing paperwork as you can for not paying the correct rates. Your certified payroll has to be submitted to whomever is writing the checks, and I don't mean the GC. If you are a sub or second-tier sub, don't count on anything making it up the food chain.
We had one of the head machers come up from the DOL some time ago to give a talk to the AFAANJ (Automatic Fire Alarm Association of New Jersey) on prevailing wage. They are very willing to help you out. They're more interested in making sure workers get paid than stringing up employers, so even if you make an oops! it's not the end of the world as long as you show a willingness to cooperate.