The "race gas smell" is actually the an additive they put in the gas. A very flammable chemical called Toluline. I work in refineries and you just walk around thru there and it smells as if you are at a track.
Also race gas will have some lead in it too, i know at least c-16 does, but im guessing the chances of u being around any 5.0 built to run off that stuff will be pretty slim, but 4cyclynder turbo buddies run that shiet all the time so they dont blow up and so they can keep up with the big dogs, I spent a day around a car running that tho being tuned in a dyno shop and drivin around it all nite and never has any fume from a car given me such a headache!!!!
i dont know what specific octane will smell that way, even though higher octanes smell pretty potent (expecially with an offroad pipe) sonoco 94 i used to run still smells like regular gas, just intense... my buddy will cut c12 with 93 octane at 50/50 mixture when hes at the track and give his vortech 5.0 a bit more timing, even that car with stock internals and heads, and cam will give you a headache following it.