Problem: Limousine too soaked in blood and riddled with bullets for quick, ad hoc clean-up = if actual condition is examined closely would reveal multiple bullets, fragments = multiple shooters; hence a large conspiracy and eventually proof of SECRET SERVICE INVOLVEMENT IN JFK’S MURDER.
Solution: Send entire limousine back to the Hess and Eisenhardt, later Ford Motor Company in Michigan and have them “rebuild it into a newer and better version”. Out-of-sight, out-of- mind. Out of danger of the American public catching on.