Engine vs Trans vs gearing

[Ultrasummer]

I wanted to pick your brains and see what you suggest. I have a 1968 short bed C10 stepside. I've had it for about 6 months now cleaning it up and fixing the minor stuff. It seems pretty much all stock. It has a 307 engine with a 4 speed on the floor. Runs great, starts right up. First gear is a granny gear and getting up to highway speed, I have no tach but it feels like about 5000 rpm. I don't want to do some crazy LS swap or lower it. I just want a cool looking old truck that is fun to run around in on the weekends. It's not my primary vehicle. It would be nice to be able to go down the highway at 60 mph with lower rpm's. Plus, I could do without the granny gear. Just kicking around ideas for now. Just change out the gears in the rear end? Crate 350? If I did either of these, would I have to address the trans as well? Oh and from what I could tell by the internet, rear end gears are 3.73. thoughts and suggestions are welcomed.