I once had a 292/292/108 in my 367. That I measured at 248/249@050
I ran it with every carb in my arsenal. No problems but, every one required a different amount of bypass air. All of them ran fine with as little as 5* Idle timing. Altho I ran in the 22>14 window, which provided enough T-slot exposure to get rid of the Tip-in sag.
If you can't get yours down that far I would suspect internal friction. In my case I had to take the engine down, add ring-gap and a tad more skirt clearance. Badaboom.