I just purchased a 1992 integra 1.8 auto trans. Stock everything. Auto trans seems to shift fine but at freeway speeds 70-80mph rev's are at
at approx 3600-4200 and car never seems to step down revs unless I
drop speed down. Already replaced vacuum mod. any ideas or is this normal range for this car.

yeah thats perfectly normal, I have a 93 gs-r and at 75 in 5th gear I am at about 4000 rpm.