If it were me, I would do the suspension and brakes first to get it up to 1970’s standards which are far better than mid fifties. Then work on the driveline. Figure out a motor and trans. If you want something with good suspension and easy maint get a crown Vic front subframe. This will get you everything you need and allow you to bolt in a newer SOHC 4.6 or 5.4. There have actually been a few that have taken a crown Vic chassis, shortened it and put the F100 body on it with custom mounts. It looked like a vintage Ford pickup on the outside but had a modern chassis underneath.
Here is just one video on it. If you search you’ll find some very in depth videos on what is needed!
F100/panther build.