Of course the best hop up is a higher hp V-4 but you say that can`t happen so hears something to think about.
These things you mention will help performance but I wouldn`t port it to 140 specs. Your 85 has a smaller bore than a 140 and would suffer in low end torque. The 1977 115 V-4 was a runner for sure so maybe look at copying those ports instead.
Also there is a mod that most people like to do to cross flows that will give you top end but kills low end. They cut a half moon in the piston skirt just like OMC did to their race motors but keep in mind that those motors were intended for closed course racing where low end didn`t really play a part so don`t get talked into that mod.

DB