Never tried and even if it's the old RB300 with the column mount it may not be possible due to arm length / overhang and the like. They do differ.
Surely a easier option would be to sell the Pro-ject as is and buy an old Rega turntable. Just a thought.
Or possibly get an upgrade Project tonearm, however the 9c fitted isn't what I would call cheap.
Replacement tonearms from the entire range of Pro-Ject turntables. Click through to see the full list.