90% of those old part sellers don't know about the Specification of the things they are selling. I think it is sole responsoibility of the buyer to have an idea of what he is going to buy.
AS SER_GTR suggested, complete your ground work before you go to any market for purchasing the engine + accessories. Just buying the engine will not work but you have to arrange the electricals (ECU, Wiring and the Sensors) all in working condition to run your desired engine.