These trucks were geared to keep the engine running in the sweet spot (roughly 2800-3000rpm) which is going to sound to the modern ear like it’s about to come apart. Remember back when your truck was built the highway speeds were around 50, so, anything above 45 is going to cause sounds to come up from the road/frame and all moving parts. What you are experiencing is normal.
Yes, there are things, such as dynomat and products like it to soften the sound some. Things can be done to the drivetrain to lower the engine rpm but being located where you are will pose challenges. Good luck, keep on having fun.
