Dave,, I am not real familiar with SBF, but if you have an old distributor laying around dismantle it down far enough to turn the oilpump drive shaft with a drill. You will have to cut the advance mechanism off the shaft and grind off the drive gear teeth to make it work. Then spin the shaft with a drill and you should "feel" the resistance if it is pumping,as well as the gauge psi increasing. If it does not, add 2-3 liters of
oil to bring the level up over the pump body .and if the pressure increases then you do indeed have a broke pickup tube, but do run the engine at this
oil level as it could hydraulic lock.
Hope this helps.
Dave