hi there if i was going to fit a dry sump system to my engine what would happen to the old oil pump does it stay or go

It goes but the place it vacates now has a pipe directly from the external pump to feed oil the normal way up through the oilways.
If it was left inplace you would need to pull out all the inards.
On the Pinto you have to make sure the auxilary drive shaft still powers the distributor and the fuel pump, although i assume if you have gone to the huge expence of going dry sump then you will already have 3d mappable spark and electric fuel pump

What engine is it on?? I looked into dry sumping a ZX12R myself and the oil pump is replaced with one in the dry sump kit which i think will generally be the case as you arent feeding oil from the original pick-up anymore.

It very much depends on the engine..... If possible its best (but more complicated) to remove the wet sump pump (reduced parasitic losses).

On my BEC dry sump installation I'm totally removing the oil pump internals (just leaving the casing as it seals the clutch housing) and doing everything externally. However that's mainly because I need to remove the oil pressure regulator valve mechanism from the wet sump pump so I can't leave it in place without risk going OTT on the engine oil pressure.... You could leave it in place just twirling round and doing very little but it seems a shame....

It also depends how your dry sump pump is driven- if it's using the wet sump pump pulley / gear then it means removign the wet pump....

depends entirely on the setup and engine etc.

There are many kits available that use the original oil pump as the pressure stage and just add a couple of scavenge stages and a feed to the old pump from the tank.

on the other had there are many kits that remove the old pump rotors and have a new pressure stage that pumps directly into the galleries.

The vauxhall XE 16v for example, being something I am more familiar with, can run either setup and both are easily available. Its generally accepted as "better" to replace the pressure stage on this engine as the std pump is a weak spot of the engine, but then so is the belt drive on the new pump...............................

no simple answer!