[TobyB]

From experience with other BMW engines, yes, the sump's not a bad idea.
If you can keep it closer to the engine, an AN-8 line will work.
Or you can use AN10, but adapt down to get into the motor.

The thing is, it can't be allowed to push pressure back against the pump
when the pump's uncovered. That'll trap an air bubble in the pump,
and it'll lose prime- or at least until the sump's completely dumped.
So you need to interrupt oil flow somewhere to get a 1- way valve into it.
Which means a block off plate,
a 'sandwich' etc- and that's a pain on an M42.

Wait- are there 'drain back' valves on an M42? I remember having real trouble getting
mine to prime when I did the filter housing gasket and the oil pan at the same time,
and the problem was that the pump couldn't prime against the cracking pressure of the valves.

So maybe you COULD have a boss welded into the filter cover, and that would be good enough...

Time for more research,
t