According to AmericanDirtBike.com, this is a photo of a 1984 ATK:
http://www.americandirtbike.com/86-560.gifIt is clearly an Evo bike in stock form.
Note the KTM TLS rear drum, just like the one for sale.
I can't pick the forks/hub on the bike in the official photo, but they could well be CR480 bits.
I do recall Horst Leitner being quoted in MXA or US DB in the very late 80s or early 90s saying that he thought the best forks ever were Kayaba's 43mm forks from the early 1980s because they had the least stiction (and that everything else could be fixed).
It would then seem likely that the '84 ATK had '83/84 Yamaha or '84 Suzuki forks & front brake on it. Triple clamps look like Yamaha to me.
As to Evo eligibility with the CR480 bits... The standard ATK is unquestionably Evo legal. This ATK has bits from its era (actually older), so they're neither "later bits", nor is it "modifying the bike to comply".