You got a pump for a gasser, which has vacuum brake assist and no need for the additional return port. The pumps may or may not be the same otherwise, so I'd be very cautious using it. The pump demand is significantly greater with brake assist and power steering, vs. power steering alone. Unless you can verify the pumps are the same, the replacement you have shouldn't be used, even if it fits perfectly. If they the same, the returns can be Tee'd. However, if it didn't come out of the box with that accommodation, I'd strongly suspect it is simply the wrong pump.