Cargo/passenger ships linking Singapore & Hong Kong in 1980

[MichaelGabout]

Dear all,

My name is Michael and I am an amateur French writer. For a novel I'm working on, I'm looking for information about the cargo/passenger ships that linked Singapore to Hong Kong a few decades ago. Actually, I heard of two lines involved, the Pacific International Line (with 2 boats: the Kota Panjang & the Kota Sahabut) and the Golden Line (with the Kim Ann).
The action of the novel taking place around the Summer of 1980, I'm trying to find intel such as the dates of departures, the class types and their cost, the duration of the journey and the itinerary of some of those ships.
Could you provide me then with this information or direct me to a site, place , department or person who could?

Hoping to catch your attention with my request, I wish you the best,

Michael