Wow, there are some nice bikes here:
http://www.vintagemtbworkshop.com/the-collection.html
Riv's take a couple of cues from the old Ritchey bikes in that they have a point at the top of the seat tube (which I didn't know was a Ritchey calling card), and of course a modified Bullmoose bar. And take a look at that 1978 Breezer Series 1 - simply awesome!
It's also interesting that so many of these had negative-sloped top tubes...
Tom