Did a compression check here are the results.

1. 120 2. 70
3. 120 4. 125
5. 120 6. 115
7. 118 8. 120

Think the head gasket is toast on the even side. Has anybody ran Cometic head gaskets on a boosted BBC in a marine application?

A better question is, Who isn't? If you don't want problems those are one of the best head gaskets available. Being procharged and from what I can read out of the post, you may not know what head gaskets are on it. The stock head gaskets can not hold up to the boost of any supercharger. I agree with PatriYacht, don't run it until you figure out what the problem is. Your compression test numbers don't make sense to me, but they are not the same and I would start with a leak down test, or just pull the heads.
Good luck and keep us posted.

The motor has been built for a blower application, assuming it has fel-pro head gaskets. I'm going to be pulling the heads next week some time. Cometic here I come!