46trucker: much has been written on this subject. Check out
Mar-K site here at the bolt and you will find where they did a lot of test and recomendations.
What ever you use just be sure to put about 4 coats on it, and be sure to get all sides including the edges and ends. Do a search in here are in the bed forum and you'll find plenty to read.
A lot of hobbist ues the Helsman SPAR-urethane...just depends on what your looking for.


1937 Chevy Pickup
In the Gallery
1952 Chevy Panel
In the Gallery
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1950 Chevy Coupe
Pictures!

I'd rather walk and carry a Chevy hub cap than ride in a Ferd.
I can explain it to you, but I can't understand it for you smile