Duster floor (the whole thing!) for free. There was a reason....
Stress crack would be my guess,but from what? Weld the cracks up after installing,and dont forget to drill holes in the crack ends.
Heck I'd use that floor. You'll find out quick enough if it is seriously out when you lay it down.And either way the old floor is coming out right? So why not give this one a try before spending money?