The perimeter frame would not be the way to go, no aftermarket company uses that setup. not even in full custom frames. I recommend using a 64-65 chevy truck frame. it's the closest to stock you might find. It has the original 4 coil spring with a rear trailing arm suspension. You can go any route you like after that. Parallel rear 4 bar with air bags is popular with tubular arms and air bags with a rack up front can drop it on the ground. The front inner fenders as mentioned are wrong from and from pre 67. If you want it to lay frame the front fenders wells are modified close to something that is a wheel tub with no inside.
You have to make some floor pans, cab mounts and bed mounts this route but nothing you can't handle There is a great book out there for the 1:1 building a C10 truck it's only about $10 ... lots of great ideas. good luck