Gas Mileage???

In my opinion you are jumping ahead. Work one step at a time - unless you just want to start over with a fresh engine build.
I thought you're running a Carter Thermoquad on a spreadbore intake? In any event, any carb can be made to run well. However I think mixing spreadbore and 'squarebore' is less likely to have good fuel distribution.
The Holley transfer slots do need to be within a limited range for the carb to work properly. - just to be clear - I agree with AJ
Figure out your timing first. Tuning is an iterative process, but if the timing is too far off, playing with the fuel air mix is wasting time. AJ wrote he guessing based on very limited info. If you measure the valve lift you will know much more about both cam and then make a better guess at compression.