Hey, I just realised that those holes are for crankcase breathing, and one lungers need to breathe a lot, or there'll be oil leaking out everywhere. They breathed into the large transmisson case.
The original crankcase breather was on the transmisson. The breather cap is where you put the oil in, and the transmisson case is also the oil resivoir. There's no oil level in the seperate crankcase.
In fact, if there's no second oil pump for scavenge, like Harlrys, triumphs ect. then the holes may also be there for the engine to cough the oil pump emitted oil back into the transmisson resivoir. If that's the case we might hafta build a resivoil/breatherbox to fit there.
If they do have a scavenge pump, then all we need is a breather and an oil tank. Ya need to ask your Gravely buddy about this stuff.