Sorry to hear about the engine noises and associated issues. I thoroughly enjoyed driving that meticulously maintained little beastie. Love those triple side drafts. I really thought you had it at the exhaust bracket as I had the same issue with my 2002.weird “zing” sound like it was coming from the motor at 3500 RPM, every gear. Two mechanics looked at it and said they couldn’t find anything, just drive it and enjoy it. Of course the noise drove me insane. I finally located the issue. In fact, it was the exhaust bracket, or lack there of. I had to fab something off the headers.
Good luck with the motor, I completely disassembled my 2800,every nut and bolt, but I don’t mess with the engine or transmission. Most everything else you can just reset and re-do,but not either of those. A man’s got to know his limitations and I’m fortunate enough to have the wherewithal to sub those out.
You sound like you have the technical wherewithal to get this done, and of course ,it’s not the destination but the journey.