I've never owned a rag top or a 67 but the 66 service manual says check fluid levels when the "top is up". What I remember from a 64 1/2 convertible I helped to restore, remove the rear seats, cycle the pump, fill the reservoir, repeat. If you are concerned, I would remove the tubing to one of the cylinders to see if the pump is working. It will be messy. That will probably bleed the line too. I think that the pump is higher than the two pistons so air will get forced to the pump when you cycle the top. Also, get a 67 service manual.