A road car needs about 15-20% power to cruise at 70mph.
Running a Subaru (or any automotive engine) at 60-70% power settings as aircraft engines need to do is not going to be that popular with its internals....
Regarding O-235s in an RV-9, the Van's figures will be true air speed at 8000ft. I think DBo's figures are more likely UK based 'low level' figures - we don't tend to cuise at 8000ft in the UK.