Where can I buy a reliable remanufactured 318 for 1971 Duster?

Ken71Twister said
I’ve sprayed the engine area where the leak seems to be coming from (can’t see vs against firewall) and I will get my endoscope out to see if I can view the suspected area before I re-start the engine.

If you haven't started the engine all the oil is in the pan, there really ain't any in the area to leak until you run it.