I would never say that the 25 isn't a good motor. It's a great bit of kit, but frustrated by the ecu. I wish mine was as strong as it!
It's just my thoughts that Scotty has pretty much got to the end of what's able to be done. Maybe it'll creap over 350 with a 3076, maybe it'll pop. Thing is, with a 3.5, you'll get more power easier, at lower boost levels, with less lag, and still very usable around town. Diffs will be fine. The front diff works in a r35, so we're not going to worry it. Main hold back is the gearbox, which if I was going to do properly, I'd get from the states from the place I mentioned earlier.
It's just my opinion, I might be jaded because I got one!
just like going to a rb30!