leaded or unleaded fuel

He's done more than change the octane numbers.
If he's racing for consistancy (bracket) or racing for best e.t (stock class or heads up grudge) different fuels burn differently.
Pick a fuel, or fuel combination and stick with it, unless someone really knowledgable about fuels convinces you to try something that might be a better match for your engine and needs.

I'm aware of three racing fuel companies that have some amount of tech info on line, and all have tech support you can converse with.
VP Racing Racing Fuels, Lubricants & Additives - VP Racing Fuel
Sunoco Racing Sunoco Race Fuels
Renegade Renegade Race Fuel :: – Racers Who Win, Pour It In!

Someplace, maybe in one of Vizard's books, I recall there was something about the effect of TEL in increasing octane had mixing in the first few gallons and less with increased dilation. Not linear.