Cup and ball

If I'm not mistaken Comp doesn't sell 7.15 long ball and cup pushrods. Just 7.234 and 7.342 inch. I just went through the same thing myself of trying to get correct pushrods for my engine. Mopar performance sells a kit that you cut the pushrods to length and has the tool to press it together. I think that is my only solution and probably yours also. The part # for them is 4007284. Or you might be able to call Comp cams and have them make a set up for you but I bet they would be pretty expensive.

As far as a different manufacturer being different on length. I don't know how that could happen since they all measure them the same way.