I have installed hedman headers on my 72 malibu with a 350 cu in and one of the pipes on the drivers side is very close to the brake line splitter box mounted to the frame.I'm worried they will rub against each other and also the heat will be too great and cause brake failure.Is this a concern and if so, is there a simple fix. Thanks in advance.

I think that it might be a problem. You might be able to move it a little out of the way. If not then I really don't know what you might be able to do.

You could make and install a heat shield out of sheet metal or aluminum. Just make sure the heat shield doesn't touch either the brake lines or the header.