Stockers are ~36#, you would probably be fine with 42.5#
Tuning is relatively easy for E85, you don't have to worry about knock, the AFR that ethanol makes power in is pretty wide. The only thing you have to worry about is too much timing and boost to blow a head gasket, you probably still won't see any knock.
The biggest thing is limiting yourself to E85 stations, you should have another pcm on hand or plan on never taking a road trip.