I have a nice Mavic rim laced to an old Shimano Uniglide 7 speed hub. I'd like to throw it on a bike for single-speed use (obviously not fixed gear because it's a freehub), but most of the spacer sets I'm seeing a designed for modern 8-9-10 speed hubs. Are the splines on my uniglide hub different, and if so, do I need a different kind of spacer?

Also, I know that the small cog is threaded on this hub and serves as a lock ring. Is it possible to get a threaded lockring, or do I just have to use a spare 12t cog as a lockring? Thanks in advance...