The 303 was the mainstay of African hunting for so long and for so many different game animals, you could hardly go wrong choosing almost anything as a pairing for the 303.
For me, purely from imagination, the medium antelopes just seem ready made for the performance of the 303.
I could envision a Lee Speed 303 engraved with a Lesser Kudu on the magazine and maybe a Grant’s or Tommy somewhere on the action, butt or grip cap.