52 GMC Longbed Bed Question

[Hawkerdriver]

The bed I was given with the truck had no parts on the bottom ie cross sills, not sure what I need to get to replace the bed, all the bed parts I've looked at do not specify whats underneath any one have an assembly manual or pics? PICS are always great... The spare tire rack also sits up a lot further than the two cross members I have in the rear? can I remove the spare tire holder for a tank possibly? I am doing a 4 link and those spring hangars are no longer needed. Any help is always appreciated.