Buy drums of it, or go to local pumps around Indy. E85 in different states and different gas stations can range anywhere from 50% to 85%. So it’s best to either have a zeitronix ethanol sensor that shows exactly what content you are running. I don’t have mine installed right now so if I ever go to the pump I just take a 5 gallon race can with me fill it up and come back home and check content. I usually go to one specific gas station close to me though because it’s always at least consistent 85%, I’ve seen it be e90 before.
Sometimes I’ll just have a clean water bottle laying in my car and use a tube ethanol sensor right at the pump, people look me like I’m a crazy mad scientist.
For most people though haltech is the way to go without worrying. Fill up and go.