Some guys have used plywood for the floors in panels.
As far as the metal strips, check with Mar-K (Phone (844) MAR-K844.) They manufacture them for the pickups and they may be able to supply longer ones that you need. They may even list them in their catalog.
Here's their worksheet for custom bed strips if they don't stock what you need. Custom Bed Strip form

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.