I missed this thread earlier. I'm working on something very similar. Tube frame, mid-engine RWD, 1500 lbs (TBD). After talking with subie friends and then people on here, I decided on an ej22t with s20 heads (were cheaper and I'm on a serious budget.) I think you'll get a good powerband with an increased compression ratio on e85. I'm shooting for something closer to 300 tq/whp, so I'm not going as crazy all out as you. Having the turbo relocated also really gets the power started early. Look at the 2010 LGT power curve.
Anyways, I think you're on the right path. I'll keep an eye on this build ...should be fun!