just an FYI
You asked about the 81's being too big....
I looked on Holley's website and most 750 cfm 4150 's are jetted around 70 on the primaries..depending on which model it is..may have been 69 or 71 that is with a power valve so yours is 11 or 12 bigger without the PV. So you are on the fat side of the recomended increase in jet size when the PV is removed.