Pardon the ignorance, but every PSU Ive bought in the last decade (With SATA) has 3.3V on the connector. (The orange wire???)
We are talking about the same thing right?
That connector doesn't have 3.3v. But I know Molex is just the company who makes these connectors, it's just the association I have.
Back on topic, to take 5v down to 3v you can use a voltage regulator like a LD1117.