I have a D6 9U 3405 converted to hydraulics and I would like to know what kind of pressure I should be looking for from the pump. I can't find any name or #'s on the pump. It is direct coupled to the lower pulley on the crank shaft and my coupling went bad and I'm replacing. If anyone would have any information it would be appericiated.

Is it a Cat set up with the pump, control valve and tank all in one unit?
The factory setup would be a #46 Hydraulic Control. The ID tag would be on the left hand side of the rear face of the tank assembly. The pump is a 70 gpm unit running at about 1000 psi with relief valve set at 1100 psi.

It would depend on whether your cylinders are as big around as the CAT ones were. If similar bore size, the pump pressure would need to be around 1000 psi for normal operation. The relief might be set a little higher than that.

Is it a CAT hydraulic control that's on it? Or does it have a pump there on the front and a resevoir and valve up on the fender like a lot of the other setups had?

Older hydraulics were generally low pressure/high volume designs. Now a days they are high pressure/high volume for a more rapid response and plenty of power.