1980 Mercedes 400SEL

t’s a 450 SEL with a 4.5 liter V8. My body is really nice with very little rust. Car was running and driving but has been sitting. The fuel hose from the tank to the pump was dry rotted and not allowing fuel to be pumped to the engine so we put a new hose on. The engine will run but shuts off when you stop cranking the engine so my guess is it would need a new ignition switch. The car I’m told is a one owner car from Rhode Island that the original owner sold my friend. My friend never registered it but traded us for a Honda we had. I can get a bill of sale signed from the guy who bought it from the original owner along with a filled out DMV affidavit form.