Ok, IMO you are at least 4 degrees too wide on your LSA. At least. IMO you should be at 102. No wider than 104. Unless you are running EFI.
Plus you are low on compression ratio (again, my opinion) so adding that to that wide LSA you kill header function.
Since I’ve seen this a hundred times over the years I’m betting your Intake Center Line is 106, which also hurts header function.
Again, IMO you could probably just run 1.75 headers and it won’t make any difference.
Or you can use the 1.875 headers because like I said the engine will be numb to header tuning.
I have an article from a magazine where Billy Godbold (formerly of Comp Cams) talks about LSA, ICL and header function. If I can figure out how to copy it and post it here I will.
You have to read the whole article but he covers why sometimes headers don’t make any difference. IMO that’s where you are.