I figured I'd post what I did to close out this thread.
I removed the lines so that I could clean the adapter on the bench and got some new seals for reassembly. I suppose the lines have to be removed anyway to get up there and scrape the old gasket off. Wow, that was tedious laying on my back using a razor blade.
The sad part is I paid someone to do this job last September because I was short on time. The shop definitely did not replace the line seals.
Anyway, I'm curious about the various gaskets out there. The one I scraped off was very thin and paper only. The one I used is OEM and is metal sandwiched between paper and much thicker.
Prior to starting the job I went to Advance Auto and picked up the Dorman kit for comparison. The Dorman gasket was a lot thicker, maybe 50%, than the GM gasket. I'm not sure if it was really 50% thicker but it was obviously much thicker, by look and feel.
I saw a lot of posts online for various LT1 powered cars that recommended the Fel-Pro kit but I couldn't find one. Is it best to use the GM gasket or would it have been better to use the thicker Dorman gasket?