So I just bought the MotorTrend issue that features the D170 build and gives a really nice send off to the Challenger platform. The history chronicles back to 1967. A must-read and buy imo if you love the Challenger, even if you are not getting the D170.
Anyhow, in that write-up and I quote here are some details on the E85 set up (see attachment).
View attachment 104642
Given this 65% caveat for the tune, before locking in on a station to fill up at for the D170, it sounds like doing an area canvas for the best E85 might be in order. At a minimum, you're gonna want 65% alcohol content. Also, if I am reading this right, Dodge had to leave some of that tune off the table since 83% might only be available in a few select places. Given that, maybe there is a bit of room to get even more aggressive and modify the stock 170 tune if you could somehow consistently get 80+ E85. Then again maybe the internals are built to only withstand operating at 65%. I'll let the board's tuning experts take it from there!
BTW they also mention something here I read nowhere else. Micky Thompson tried to "bow out" since they weren't sure they could produce 3300 x 4 wheels for the car. In the end, Dodge convinced them to stay. Given this I plan to buy a set or two as soon as I take delivery of the D170.