Yeah usually bottom ends go on rebuilt motors for some reason. Stock blocks are pretty strong and another 40 or 50 hp should not be a problem for your motor. A good tune on e85 should result in little to no knock. One thing to keep in mind is that cold weather e85 is actually a different blend and not true e85. Cold weather "e85" has less ethanol. I don't remember if crbquist mentioned if he would be driving in cold weather or not.