Does anyone know where I can get hold of a 28 hole rear hub to fit a shimano 7 speed cassette? preferably silver, ideally dura-ace?? Not sure of the spacing of my rear dropouts but it's a 90's trek so probably fairly standard i hope.
Maybe just trawl eBay for a while - most things come up eventually.
7-speed Dura Ace hubs are oddball though. They were only made for Uniglide cassettes, and the DA Uniglide threaded locking sprocket had a unique thread. Needless to say, they're rare now.
Shimano 600 hubs came in a 28h 7-speed hyperglide version (model number fh-6401) - that's probably the best hub for you. There's one here, but I can't tell whether it's the Hyperglide model or the earlier Uniglide one - you'd have to ask the seller:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0221248646
You could also consider a freehub body transplant on a later hub.