You can get 5 gallon's of VP Red from any dealer. I can even get it from local gas stations that sell it for less if you bring your own can. Most speed shops sell it as well.
I run a lot less octane than most. I mix 1/3 VP Red with 93 octane with a 12:1 & when I took it apart this winter it looked like new.
Run the least octane for least cost but the most power.
Listen to the engine for pinging/knocking. It may be hard to hear under a load but if you are jetted correctly it will run real hot if you are running too low of an octane.