360 stroker oil pan leak, pan out ready to re-seal couple of Q's

I always use gaskets. The plain old-school cork with rubber ends. Only two things cause a leak: the gasket installation (not choice.. just the installation) or some other influence on it that the gasket was not designed to seal. In most cases it's lack of ring seal, or blow-by that is pushing the oil out and that's the spot that's weakest. Did you do a leak down on this thing at all? That will tell you if the rings are sealing or not. In other cases it's surfaces that are not clean and oil and grease free. That includes oil from your skin. All surfaces have to be cleaned with solvent before the gaskets go on. I use weatherstrip adhesive to glue the cork sides on the pan after the rubber end seals are on it, then a little ultra grey RTV on seams and corners. I torque evenly in steps "from the center out". Be careful not to over tighten.
No engine "needs an evac system". They all need some form of airflow through the crankcase. There are thousands of longer-than-stock stroke engines running stock PCV systems with no buildup of crankcase pressure. Some guys like the header evac systems, some like just breathers, I've always been partial to the PCV system. But nothing will work 100% if there's blow-by of any significant amount.