Green’s Dictionary of Slang

(US) a very fast vehicle.

1966		Times Recorder (Zanesville, OH) 13 Mar. 10/5: This honker looks real sanitary. I’ll bet she’ll hum.
1975		Sing Out! July 8: There’s nobody there now, they are all on this honker [HDAS].
1980		A. Pearl Dict. Popular Sl. 72: Honker n. (auto racing) a particularly speedy car [HDAS].