That's a big project!
Is this an Advance Design or an Art Deco truck?
The track width of the '73-'87 is a bit wider than your '47 regardless of which body it is.
If its an Advance Design the wheel base is 137 inches. The C20 pickup is closer to 125 inches, about a foot shorter. You'll need to lengthen the frame about one foot.
And of course you will need to build body mounts and connect all the controls.
Its a lot of work. I'd suggest starting by looking at how that body will actually fit over the wheels and tires before choosing a frame donor.
One more thought. A '73-'87 C20 is a 3/4-ton truck. It won't ride like a new car no matter what you do to it.
