First, others will correct me if I'm wrong, but E85 is just a fuel, not magic. You can exceed the detonation threshold on E85 the same as pump gas. The tuning method is the same for both. We don't have e85 around here, so I'm kinda stuck anyway.
The point is that the rods will suffer from knock/detonation, and the bearings from overrevving. These are not fuel specific.
Granted, you can run a lot more timing with E85 before you hit the knock threshold, which is kinda magic.
I installed a Walbro 255...it's a very standard fuel pump for increases fuel needs. There is a high pressure model which is the one I got.
Running E85 requires more volume per hp. So, while I suspect you'd be fine with a 255 at 300ish hp, if you decide you want more you may run out of fuel. Other will have a better idea on that.
I like higher fuel pressures...50-60 psi for turbos. It gives you more pressure 'headroom' as you run higher turbo pressures, and probably atomizes the gas better etc.
I have a stock reg that runs at 50psi WOT with the walbro 255...didn't feel that I had to go adjustable. However, it is a GSR reg-they were a bit higher than the stock B18B1. I'd get an ebay adjustable fpr 'hat' and run 50-60 psi if I were you.
500cc+ injectors for 300hp, or 750s or 1000 if you want to go for more hp.
ECU. I have a OBDI ECU and a S300V3. Yeah it was expensive. I looked at chrome etc, but I'm really glad I got the S300. It really is a Cadillac and worth the money. Although it was painful to get the money together, I don't miss the money and really like the features of the S300. I soldered in the 'chip kit' myself, but I do that type of thing quite a bit--If you're not familiar with soldering then it might be better to get a 'chipped' ecu, and I suspect you will need a wiring adapter-OBD1 to OBD2.
I used a cheap ebay piping/couplers (that turned out to be pretty good quality actually) and intercooler setup (CX racing kit). It seems to work well at my hp (Under 300). I had to modify the piping for my custom turbo setup but I have the advantage of being able to tig weld aluminum so it was no biggie for me.
Hope that helps.