in theory just adding the overdrive ratio of .70 you should be turning 2100 rpm. Thats without a lock up convertor clutch. if you add lock up i'll drop it about another 200-300 rpm, maybe a little more. alot of the f-body guys go with 3.73's. get down below 1500 your just going to be into the convertor stall so much it'll nuke it.