well, thanks Curt but I'm headed a different direction for the moment.
I've made some gaskets out of FelPro high temp gasket paper and I'm going to run it tomorrow to see how that works.
When I got in there earlier today I could see that the portion of the flange directly under the bolts was flush with the head, but I could see a gap where the o-rings were. In other words, can't tighten the bolts any more, and the o-rings are bulging the manifold away from the head. Not good.
So, I see where washers would be some help here, but I thought I'd try for a permanent fix.
Will report back