As far as the pump nipple and pump operation goes, yes you can just use the cover plate from the old carb. On the new carb, there is also a hole on the mating flange between the carb and the reed body that will need to be plugged or blocked off by the flange gasket. You can do this with either a gasket that has no hole or block off the drilled hole in the carb body with a bit of JB Weld or equivalent.
Regarding whether the new carb will work correctly on your engine, I have no way of knowing that. What is the # of the new carb and where did you source it? A new one from Tower is less than $40 and it comes with the correct fitting. Replacement fuel inlet fittings are available from a number of sources for around $5.00 and this includes the plastic ones like you had or all metal ones that are nearly indestructible.