RPM at 70MPH

Don't remember what diameter tire, but I swap between something like a 235/60/15 and 255/60/15 (pure street vs. street slick) and with the smaller ones I used to turn 2500-3000 easy with my 3.55 rear gears and the old 4 speed. I've since swapped to a T56 with a 0.5:1 overdrive and now cruise around 1750 at 70 mph. It'll lug a bit if you're one a steep hill or lay into it hard, but that's what the other gears are for. I don't think you'll hurt one cruising even at 3k, but it's a little nicer on the ears and peace of mind to bring it down. New engines are pretty amazing with longevity and taking punishment. Have taken apart 1 with over 250,000 miles that didn't even need to be bored and another with 160k+ that regularly ran with only 1 quart of oil in the pan that only needed to go .020 over.