Here is a list of Harleys that have the 2240:60 ratio:
1984 - 1986 Wide Glide
1984 - 1995 Softail
1986 - 1990 Heritage Softail
1986 - 1995 Softail® Custom
1987 - 1995 Heritage Softail Classic
1989 - 1995 Springer Softail
1990 - 1995 Fat Boy
1993 - 1995 Nostalgia
1995 Bad Boy
J and P Cycles sells the speedo in question. They also sell a rear speedo drive setup that can be modified to work on a CB750 (havent done it, but it seems like you'd just have to bore it out a bit and adapt the small hook to your sprocket).
http://www.jpcycles.com/Search/ProductDetail?sku=5600262&N=0&Ne=0&Ntk=All&Ntt=2240%3a60&Ns=&results=10&Nao=Here is a picture of the Acewell on my bike:
It definitely does not feel cheap and looks great. I've been having some trouble with the engine so I havent put enough miles on it to test out the display. The casing is completely waterproof and if you go to Acewell's main Euro page, you can see they have a display of them operating in a fish tank. The mount is small but pretty solid. I made my own so that I could fit it in between my bars. The wiring harness is top notch too and even though it has a lot of wires, it doesnt take up much space at all. As for the speedo pickup, that was easy to run as well. I had to make up my own magnet to stick onto the rear sprocket, but I havent installed it yet. You might be able to run it off of a magnet on the front sprocket, thus being able to hide the wire more easily. I'm not sure how what the upper and lower limits are for the rolling radius that you have to put into the speedo to get an accurate read though.