I can't comment on the Dolmar, but the Husky is a good saw. This might be overstepping a touch, but the Husky 77, 180, 280, 380, and 480 were all reincarnations of the 77cc displacement platform that Troll alluded to (one piston fits all!). Of all of these, the 480 seems to me the most common. If you just have to have the 77cc Husky and you're looking for a saw you're actually going to run, that's the one I'd go for as (IMHO) I think parts may be less of an issue. They also don't seem to command a terribly high price, as they are eclipsed by their larger brother, the 2100. Some would argue (me?) that if you're looking for as much boom as you can get in an older Husky, you might want to just keep your eyes out for a 2100/2101. You'll definitely pay more, though.
The older saws are great fun, and they are worth having (I tell myself).. on the other hand, if you really want a working saw, say, for milling, I would look into a used Stihl 066....part, parts, and more parts.