Turns out my 300 dollar '75 W115 300d has a knock -top of number five piston is bright and shiny from making contact with the head, If lucky, the crank journal will be fine and we can install new rod bearing, etc or it might be wrist pin possibly. Anyone out there have any leads on a running '75 or '76 w115 300d engine? Help! I wish the 123 engine would work but the block set up is different . . . . .