so i went to put my dually bed and stuff from my 77 ext cab to my 78 crew cab but the frame appears to be 3 inches narrower on the crew cab... any explanations? thanks

 

I just got schooled on this earlier, your frame is similar to one from a high boy, they are narrower than the rest.

 

this throws a small wrench into my plan... guess ill have to make some brackets now thanks!

 

Dually frames measure about 34" wide outside to outside to allow room to mount springs due to dually offset, about 5". I was told a long time ago that the 350 dually frame was narrower than the 250 frame but never saw for myself.