Depending on what you are used to driving, that kinda RPM might seem quite high and by todays standards they are. These older trucks were not built to run at higher speeds but if you 'adjust' some things they will do pretty well. I would change that ring & pinion to something closer to 3:00 for some better top end - knowing you're going to lose a little low end pulling power. But finding an older trans with the overdrive in it would be the ideal setup.