Thoughts on this combo for E85

I have a 408 short block that I've had built for a while with a forged 4 inch crank, eagle rods, and Icon 4.03 bore flat tops with valve notches with zero deck.Problem being that I built it in a magnum style block (don't ask what I was thinking)which means with the closed chamber Edelbrock Magnum style heads I have it will be pushing around 12.2/1 compression. I also have a Edelbrock Performer RPM airgap and a Comp cam part # 20-746-9 which has 506 lift and duration of 265 on intake and 273 on the exhaust. I am trying to salvage my mistake with the compression and maybe try to run this thing on E85. This engine is going in a 1970 Dart Swinger with an automatic trans. The car is an original air conditioning and power steering, power disc brake car and I plan to retain all of these options. I will be running 3.23 gears and plan on driving the car a lot. It will probably never see 6000 RPM. I would like to know what the current thought is on this combo and what could be done to improve on it. I already own all of these parts so I am trying to use them up. Also would love to hear any advice on running E85. Am I barking up the wrong tree? or should I back up and punt?