I encourage you to call someone who specializes in this area for a quote and a detailed explanation of what is involved. I use Wheel Works here in Southern California but
http://www.buchananspokes.com/ is well known. Excels are available in silver for vintage i.e. drum brake bikes so I had no problem with putting one on my 1983 CR480R for about $250 "all in". I am remembering that you might need to have a silver rim anodized or powder-coated black because the stock ones in black are not for drum brake hubs. That being said, there are plenty of vintage bikes around with black rims so it can be done.