I thought I had already responded to this, but I guess I didn't. You can order, very inexpensively from Harbor Freight an aluminum welding rod that melts at very low temperatures, so a propane torch is all you'll need to use it. If you cut small aluminum blocks, drill and tap them, it would be an easy job to tack each one to the proper spot behind your dash. I used this rod to build my aluminum battery box, which is as strong as any welded with "proper" rods. The only caveat is, aluminum is an excellent conductor of heat, so you'll need to protect the welds you've just made, from the welds you're about to make. If not, you'll see your completed welds puddle away. Aluminum doesn't discolor like steel does when heated, so the finish on your dash won't be harmed. Weld and install. No cleanup necessary.
If this isn't to your liking, duct tape is always available:)
Bruce