AvGas is pretty much the same complex blend of hydrocarbons as race fuel but has it's octane calculated differently.
100/130 for example is a take-off and cruise octane number which doesn't compare side by side to Motor or Research octane numbers, but the lower is closer.
The Reid Vapor Pressures are different also because of the altitude (atmospheric pressure) that it needs to vaporize at. So, don't buy Avgas in winter for use in summer and vice-versa.
In most cases, you won't need to use AvGas or Race fuel at 100% anyway..
For years I easily got away with a mix of 66% 92(R+M)/2 with 33% 100/130 AvGas in my 12:1 BBC with no adverse effects what so ever and with ~40° total.. My engine cranks 225psi during compression tests and also has a knock sensor.
When it was dynoed (engine dyno) it made just slightly more power on the AvGas that I supplied as opposed to the VP fuel the dyno operator supplied. We made a few jet changes as well and the AVGas results were better. OK, splitting hairs, but still better. That has nothing to do with octane though or which fuel is "better". That's probably just a case of the particular blend of AvGas I supplied had a higher specific energy in a given volume compared to the VP and showed that the AvGas was still quite capable of producing power in a large bore automotive V8 engine, like the VP.
Basically, what I am saying is AvGas is fine, but don't go by it's octane numbers and use it in the same months that you buy it..
Anyway, a better option is water injection. I have a Snow N/A kit and with 92 octane I am still get detonation free with 38° total advance with 12:1 and the same ~260° solid roller. You can add 50% methanol to the water if you want for even more resistance and a couple of ponies.. I am yet to try it. Water is cheap and easy.
