Does anyone know what I need to do with my 1999 Chevy 1 Ton with a 454 engine for it to accept E85?

Right now I am running 1/2 and 1/2. 1/2 reg. and 1/2 E85.

Not worth it man. You need the newer intake gaskets, higher flow injectors with higher flow capabilities, and your pcm has to be compliant with e85. In short you have to have the capability to flow more fuel and the electronics have to know it. e85 has to have more fuel to burn at the right ratio, hence the worse mpg. You will through lean codes with you current setup. I can't believe you aren't already running that blend. The fuel trim isn't capable of a whole lot of fuel delivery change.