Yes! I ran a 2mm skim on a 7.5:1 head and a knife-edged butterfly and slimmed splindle in my 650 back in 92, and with no other mods, saw 75 on the flat! If I'd done it with the 8:1 head it would have been better.
Probably the biggest regret though was the ignition. If I'd have been able to get EDIS as with Megajolt/squirt then I'd have got 60-65 to the gallon too! Programmable ignition has to give the greatest return.