Tarantino did not 'rip off' Wild at Heart
If anything he was ripping off Alex Cox.
There is far more of Repo Man and Straight to Hell in Tarantino's work than anything by Lynch. In fact you could even say Lynch was ripping off Straight to Hell as much as Tarantino was ripping-off Lynch (n.b. contrary to popular belief Lynch did not invent surreal, slightly perverse or off-kilter depictions of classic Americana, he just popularized it).
Straight to Hell, with its exiled hit-men (one white, one black, both dressed in black suits and skinny ties) lost in a harsh and violent desert; where desperado's wage war with them; where seductive, possibly insane women want to sleep with them; where elements of film noir and spaghetti western are merged; where the dialogue is peppered with pop-culture references and pitch black humor; where the entire thing teeters between insanity, tongue in cheek farce, genre deconstruction and political satire.
There's more of Pulp Fiction and Wild at Heart in that description than there is elements of Lynch in Tarantino.
Tarantino's early style was essentially the cinematic approach of the French New Wave (early Godard in particular) combined with elements of film noir, Italian exploitation, Hong Kong crime thrillers, B-movies and the work of "new Hollywood" directors like De Palma and Scorsese.
Wild at Heart seems familiar only because it's Lynch's most post-modern film (it shares the same influences, chiefly youth on the run exploitation movies and Italian westerns); his other films tend to be more like distortions of classical Hollywood movies (Sunset Boulevard, Double Indemnity or Kiss Me Deadly filtered through influence of Cocteau and Maya Deren).