Well, it’s just my opinion (and you know what they say about opinions).
I think you would get a little more buyer interest in the Nordic but it is also a good vintage sled to keep from a collecting standpoint. Based on your description it could probably be priced in the $800 - $1200 range in running condition.
The TNT is a bit of a mystery, as there doesn’t seem to be that many around. In non-running condition, I’m thinking maybe $300 - $500.
The Blizzard 5500 would definitely be the lowest maintenance sled (better carbs and CDI) and should also be the fastest and the best riding by far if you were to keep that one. A lot of these get converted to drag sleds. If it were me, that's the one I’d keep. If it’s a good runner, I’m thinking somewhere in the $900 - $1500 if you decide to sell it.
As always, it doesn’t hurt to start high and negotiate but there will always be low-ballers and buyers you can never please. I’ve had guys say “it can’t be that nice if that’s all you’re asking” and others say “You’re asking way too much” – on the same sled.
Of course, based on my past behavior, I'd probably keep all three
