Confusingly, the anonymous Wikipedia writer also stated that Micky Dolenz sang lead vocal on "Down the Highway" (as allegedly "mis-titled" on the Missing Links, Volume Two album), but, clearly, the recording entitled "Michigan Blackhawk" on the CD has Nesmith singing lead. The Rhino Records CD liner notes declared the song to be Nesmith's "Michigan Blackhawk," but the unknown Wikipedia author disputes this as a track listing error. Another source provided purported studio recording logs for "Down the Highway" (recorded June 5, 1969 at RCA Studios in Hollywood; composers' credit to King/Stern) and "Michigan Blackhawk" (recorded June 10, 1969, at RCA Studios in Hollywood; composer credit to Nesmith). This source also mentioned that Rhino Records released "Michigan Blackhawk" on Missing Links, Volume Two.
I'd have to hear both songs to be certain, but I can't find a recording (or lyrics or sheet music) identified as "Down the Highway" (crediting the song to Carole King & Toni Stern) anywhere on the web. You'd think it would be somewhere. ASCAP? Carole King's official website lists the song as copyrighted 1972 ColGems-EMI Music, Inc. (ASCAP), but the site says lyrics are currently not available. Maybe I should email Nesmith at the Videoranch. Or Carole King. Not much chance their minions would answer my email, though.
In the irrelevant aside department, the lyric "moving along the highway" appeared in "So Far Away," by Carole King, on her LP Tapestry . I'm presuming that we're not talking about a Monkees cover of "Down the Highway," by Bob Dylan, from The Freewheelin' Bob Dylan (1963).