I'm looking to put a cap on my truck. I've found one I like on Craigslist but it is on a 3rd gen and I own a 2nd gen. both trucks have 8 foot dually beds but I hear that the top rail dimensions might be a little different.

 

Drive to it and see if it fits.

 

if you search the web you can find bed dimensions for every make.

I have a 3rd gen single cab long box...I can measure my box for comparison.