I installed a Bastuck 3.7 ratio in my 3A a year ago, and it was a perfect fit with no drilling required. I think it's the same part for a 4A (correct me if I'm wrong). I purchased from BPNW because at the time it was much cheaper than the same Bastuck part from TRF. Neither vendor mentioned anything about an Italian part, but maybe that's just for the 3.45 ratio, of which I have no knowledge.