Purchased this machine last year and am now the third owner. Came with two pony motors as I was told the one in the machine was not functioning and that the second pony was on a skid to replace it. 
Unfortunately I assumed wrong and have now broke both motors and am in the process of rebuilding one out of the two. Considering the electric conversion as well. My question is this: with the pony motor out and stripped down, it appears that the bottom of the crankcase has had the casting knocked out on both engines in order to allow oil to be shared? I have looked at several ponys that came out of D4 units and they do not have this other opening on the bottom of the block. I thought there should only be the one for the coolant and the oil in the pony was isolated as a stand alone. 
Anyone able to tell me if the coolant and the oil should have passages on a D6? 

On the D318 (D6), the pony crankcase bottom is the clutch housing top along with the crankcase drain through the clutch housing. There are no connecting oil passages to the main engine.