Bed cover

[70stroker]

I’ve been looking for a fiberglass bed cover for my 6.5 bed Dually. I found one (and only 30 miles away, and the correct color) which never happens for me for only 300.
The guy said it came off of a 05 ext cab with a 6.5 bed. Does anyone know if this would fit my 99 6.5 Dually okay?
Thanks in advance.

 

[98chevy2500SS]

I believe the rails are wider on the GMT800s. It will fit, but it won't look very good.