You pretty much would need to get a machine shop to help you out with this. I was lucky enough to have a friend do mine for me. You can get the measurements from the EQ6 yahoo groups, where I got mine from. If you want some images I can give you a couple.
http://www.theastroweb.com/astronomy...0406%20001.jpg - My top plate prior to drilling the 4 holes to attach to the pier head.
http://southcelestialpole.org.au/for...ach=6417;image - The pier with the EQ6 and ED80.