Actually I assumed the compression increase from the 78 L-48 (8.5:1) to the L-82 (9.1:1) was due to the different piston design. I didn't realize there was a thinner head gasket. I did some research and I've read the L-82 originally came with .018 gaskets... Eric may be right about .015 also.
But the .026 gaskets interest me. Maybe this is a dumb question but should I have a detonation problem with the Summit cast iron cylinder heads and .026 gaskets or should I stick with the .039 gaskets bringing it to about 9.1:1??