My Lancair-235/320 (150 HP carbureted and Bendix mags) with an Aymar-Demuth 62 X 78 fixed-pitch prop does 180 KTAS + at 2700 RPM full-throttle at most altitudes up to 10,000' while burning up to 9 GPH down low and decreasing with altitude increase.  No fuel-flow gauge so don't know the exact fuel flow numbers for sure, but each 100 RPM equals about 10 KTAS below 8000' and a corresponding decrease in fuel flow. . .  I carry 54-gallons and have flown as much as 6+30 while covering a distance of 960 NM (San Diego - Seattle with the typical summertime headwind) using a power setting that resulted in 170 KTAS at 10,500' and landed with 4 gallons remaining.