I'm sorry your 81's wont do more than 55. My '81 takes me to my cabin in the Pocono Mts 65mi. each way every other week 9 months of the year. Interstate 78,33, and 80. Left lane most of the drive. Qjet with no choke. Never a problem starting hot or cold.
Fuel injection and overdrive? Not needed. Guessing a malfunctioning q jet. I would have had it rebuilt. That lift will create as many problems as it solves but it's your truck and your vision. Looks fine as is.
Glad both of my squares are Natural patina trucks. So much more to consider when you are going for #1 or #2 quality. Fit and finish is the last thing on my mind.
I've had/have a few 400's in my day. They are good torque motors and that's where all of the fun is. That truck wasn't designed for 450hp. Agree with others to not go crazy with the cam.
Expect 10 MPG while driving the wheels off of it. Your $3,000 will turn into $6,000 in an instant. Just so you know what to expect when investing in a vehicle like this.
There is a guy near Lancaster PA that deals in rust free southern beds. Also spring Carlisle would be a good place to look. Would save a lot of work and $ to just swap it out.
I'm surprised that nobody mentioned a leatherman. I never leave home without one. Don't try to take it on the plane, they will take it for sure. My favorite one is the "Blast".