I have RPM 70 cc heads on my car. I drove it about 1500 miles before the blower and they worked great. 12,000 with the blower so far, same gaskets , same plugs. I do use head studs which require engine removal to service the heads. My choice however. Mine were new but purchased at a very long deal.
There should be a number on the front of the heads. From this you can go to the Edlebrock site and find what cc they are.
With an Edlebrock RPM cam and roller rockers you are limited to about 6500 rpm and about .560 lift. More than enough for the street. The RPM cam needs a 3000 converter to be really easy to drive. I tried it with a 2000 converter and it was possible but not real easy.
They are very street worthy and limited race use. They seem to buy some leeway as far as gas octane.
There are at least 6 users of these in the groups I travel with and nobody has had any problems at all with them.
Be sure to use the correct gasket. Check the Edlebrock site.
BTW the matching RPM manifold is an excellent choice for the street. I have an Air Gap that I originally used. It worked really well but it's not the best choice for Minn weather. The standard RPM manifold will make the same hp with in a couple and be much more drivable when it is cool with the heat riser port.
I also used a Holley 3310-3 carb. It took all of the tuning aids to get it where I wanted it but it worked very well. Even got pretty good mileage. Funny thing is that the exact same motor with the 6-71 blower and 2 750 dp actually gets at least as good mileage.