Do more research. Is the truck drivable for six hours? Are the brakes in excellent working order? (If they're not, who cares how it runs?) Is it still original? (If so, you're not going over 50 mph for any length of time.) Hire a local mechanic (local to the truck) to give it the mechanical once over and pronounce it sound and ready for the trip.
I would beg, borrow, steal or rent a trailer. You do not want to discover the truck's problems on the highway. Find a friend who has a truck and trailer and will either loan it to you or go with you. Pay someone to pick it up for you.
You're talking about a 60+ year old truck. It's a very rare truck (unless it's fully restored or VERY well maintained) that can make a six hour trip without incident. Then your six hours becomes seven, or eight, or an overnight stay, and you're wondering why you bought it to begin with.
