Replacing floor drain bowl in basement

[carpnet]

I live in a 48 yr old house. About 3 yrs ago the sewer backed up into my basement. The city supplied me with a "check ball" (see attached) to screw into the floor drain threads. But unfortunately the bowl is very rusty and "ball" would not screw in. Tried cleaning the threads with a rotary brush but they are in too bad a shape. Is there a way to replace the bowl or a better way to clean the threads?

[jadnashua]

I think the only threads on that are on those wings which have some screw holes to hold a cover.

[Redwood]

I would just plug it with a "Test Plug" AKA "Dollar Plug"
There aren't any threads there!

http://www.oatey.com/apps/catalog/instance_assets/images/catalog/productimages/mechanical_test_plug.jpg