Search Contact point for purchase Opel Motor 20E

Servus. I’m looking for an engine for my ’72 Manta A. Built-in/registered is a 20E. advertisement can be found in the market place. But why am I posting here? Who can immediately suggest me a few good contact points? Either on the net or also a workshop of trust? Not necessarily in the Nuremberg room. Because I don’t want to just wait until someone gets in touch, but look for themselves. Would be nice if my skate could be pulled out again this summer! Thank you.