Caps no. As for what it cost, there's to many variables to get an answer for that. If the rails are bad enough to need replacing, what is the condition of the metal they are attached to ? Put it this way, it's a major project to replace rails the right way and not going to be cheap. If you're looking to go cheap on a car the best advice is spend the extra money upfront and buy one not needing rails.
The biggest thing I see in the Mopar hobby, and other makes, is so many people want these cars but they don't realize an old car is expensive to restore, especially paint and body. Paint materials are thru the roof and quality repair men aren't cheap. There are hobbiest who can do their own body work and it makes it more affordable to buy an average car needing frame rails. To them it's a challenge and fun. But to the most of the hobbiest not being able to do metal work you rely on the restoration shops. So unless this is a rare, Hemi, or some other "great to have" car you just have to have, I'd say spend a little extra for a solid car, they're out there.
