I have one of the "Cali Wheels" issue.
I traded the Chrome steelies for Modifies Dualies .
I also stretched the frame. to fit an 8 ft bed.
But it is not getting a Pickup bed.
It is getting an Open Road Mini-Motor Home body instead.
Here is the build so far;

Tires are OLD AMT Turnpiker Rubber Firestone Darlington Gum Dipped!!
Front Steelies are from the 64 "Cameo" kit, rears are the Chromies from the 65 bashed
with Deep set rings to make duallies. (Only the centers are from the Chromies!)
Dog-Dishes are from the 64.
Now to find the space and get back to the build!!!!