I'll share my story. Bought the '65 C20 in April 2015, and the PO told me he had rebuilt the rear end, so I didn't mess with that, just changed the gear oil. I did replace the unreliable Edelbrock/Carter AFB carburetor to a 1968 Q-Jet, replaced the plugged 2-row radiator with a new 3-row, water pump, driveshaft, and swapped in front disc brakes. Rebuilt the Saginaw 3-speed with BWOD, and this was done by June 2016 before taking it on it's first 1000+ mile camping trip. We clocked 1,300 miles that trip. Crossed over the CA/NV state lines 5 times on that trip. Fast forward to 2017, I was getting married and the truck needed to make the trip to Texas and back. I did not trust the engine, mainly the heads. I had a spare set laying around, so they went to the machine shop, and while they were being done, I resealed the engine, replaced the camshaft with an old school 300hp/327 grind, and while it was down, I also installed a new fuel pump, and new hoses. Too many little events happened that kept me from working on the truck on a daily basis after work, and it got down to crunch time. Once it was all buttoned-up and the cam was broke-in, I test drove it around town for roughly an hour over the course of a couple days, and fixed any leaks that may have showed up, and adjusted things that needed adjusted. I changed the oil, checked the coolant level and brake fluid level, loaded it up and the real road test was leaving here on a Saturday afternoon around 15:30 and arriving in Holbrook, AZ around 02:00. Luckily there were no issues. No oil burned or leaked, no coolant loss, nothing failed. Back on the road at 08:00 to pick-up my wife to be in Albuquerque, NM and she rode with me the rest of the way to her hometown, and we got there around 02:30 Monday morning. Long drives, bad seat, no power steering, unfamiliar roads and driving speeds I would not normally drive the old truck, but with the overdrive it could do it and stay under or at 3,000 rpms depending on the traffic we were cruising with. We did the whole trip without any issues except needing to replace the rear bumper bolts to make sure the bumper stayed attached to the frame.
I believe your truck will do fine as long as you make sure it is roadworthy.
