In a SBC circle track engine, that had a very nice pan with a kick out, windage tray, baffles, etc......it lost 35hp by having 2 qts too much oil in it.
I would expect an over fill of 2.75qts to make a very noticeable impact on power(down 30-50hp at the upper end of the power curve wouldn’t surprise me).
It’s the kind of parasitic loss that would show up as poorer bsfc numbers, and would get worse as the rpm went up.