CAD model creation, reverse engineering and modification of pump housing

CAD model creation for injection mold. I have an existing pump housing which needs to be modified to improve strength in some areas. The new part will be very similar to an existing pump housing (which is not strong enough currently). The part is the top half of a pump housing and has 2 threaded portions and 4 holes for screws and 1 hole for a rotor shaft. Initially, I need some rough design work so I can start getting a few quotes, then if that goes well I will need more detailed design work done in order to get the part manufactured.