Ok I'll jump in...my 69 came stock with M20 and 3.23 rear. I do find myself looking for 5th gear when I get on the freeway but I think part of it is because we're not used to hearing so much sound coming from the motor in any car. I run 3100-3200 RPMs at 70mph. My daily driver runs almost as high but nowhere near the audible feedback. I run pretty short tires too( 235/45/17). 3100 isn't really that fast but it will wear on you after a couple hundred miles. We won't talk about gas mileage.