Wendell, sounds like you have a pretty nice package with the '58 235. Two thoughts come to mind; One, our old truck are noisy and all drivetrain/engine noise is amplified compared to the modern vehicles a lot of folks drive. The engine likely isn't turning the rpm it sounds like it's turning. Two, any chance it's in second gear and not 3rd when 35mph sounds like the max speed.
Adjusting valves may well quite things down (lots of post on this site with instructions). Also Tim is right, a tac will tell if rpm is excessive. I'd call high 2k excessive for cruising. If you have a timing light with a tac function it may be possible to get creative and use it as a temporary tac while running down the road a mile or so.
Good Luck
RonR
