Replacement bed support rail

[chevymotocross]

As you can see in the pictures, my rear bed support rail is in awful shape. I am nervous putting a heavy load in the bed, since it looks as though it could collapse! I'm finally going to take action this Spring, removing the bed, that rusted beam, and installing a new one. A local shop, which sells replacement panels and parts for the 73-87 (Auto Body Specialties Inc), has a beam, but the dimensions are slightly different than the original. The stock beam measures about 3'' tall, 1 3/4'' wide, and about 71'' long. Frame rail to frame rail is about 59'' at this location. The beam, shown in their catalog, which I posted (part number C-431) is 3 x 3 x 59. The height and width are close enough, but the length is obviously off. It's the exact length of the frame, so I guess it will work, but there won't be any excess beam from the frame rails outward. Would this be a structural issue? Also, not having the excess beam from the frame rails out could be a good thing, since I want to add drop shackles and I would have to notch the excess beam anyways. Also, the beam they sell does not have the holes drilled, I'm going to price up what it would cost to make my own, versus theirs priced at $49. What do you guys think?

[Slonaker]

I would consider buying an 8 foot stick of thin wall rectangular tubing from a steel yard if theirs is only going to be "close." At least it would be long enough. It would probably be stronger, and take longer to rust out next time.

Slonaker