Well, I have been by there twice this past week. Highway construction right at that site. Made pulling off for a relaxed photo attempt not a good idea. Typical of Montana road work situations.
Take exit 65, head north toward the river and right at the stop sign, which would be east. Then you see the highway bridge. At exit 66 again head for the river which is north, cross the BNSF tracks and onto old US 10. Head west (left)at the stop sign on the old highway. Until you see the closed off bridge. Good Luck