Its funny how all the things you wanted when you were young always seem to keep their appeal. I would love either a 85 model XR500 or a 79 twin shock XR500.
I remember the add for the 85 ones..."only the tough will inherit the earth". Always thought they were cool.
Those ATC's looked pretty good. A IT490 would have a bit of get up and go!

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Looks like a XR350 motor in them?