We use different ways to get the oil on original engines out, more complicated and less. An easy way is an adapter like this:
You can route the oil out pretty easy through your oil filter adapter, go then to a remote adapter, like this:
You still have the same filtering. Then you can go through a thermostatic control....
...to your, e.g. oil cooler with fan mount, mounted beneath the Bus, in front of the torsion housings. Or you'll use a front oil cooler that is only cooled through the pressed-through air. Don't forget to blueprint your oil pump to case bores, as the dimensions and positions are slightly different. A good tip is, to underlay the pressure spring/s, to get more oil pressure. When the thermostat opens completely, the oil pressure will fall down a bit, as the routing to the front or to the fan-cooler is pretty long. A self-made adjustable mount for the rear oil piston is helpful. We use a second spring. Don't forget to attach a thermo-switch to get the fan running at a special temperature. I use 87°C-92°C switches from w/c engines! Hope, this helps!