I made the gauges as I wanted to use as much of the original bmw cluster as possible. The gauge bodies are made from some 5 inch aluminium pipe turned down to the right size. I mounted the original speedo and rev counter motors on some acrylic sheet and trimmed it to size to fit inside the body.
The dial faces are vinyl stuck onto the acrylic and then some clear arcylic was used to seal the gauges along with the chrome trim ring.