Hello mate,
I'd found a meter scheme of S15 in japanese site:
In fact I can't find enough information in the 2 pics you posted. I see all meters share (24) and (28) so they must be +12V and GND, ut don't know which one is which. tachometer singal is 19 and I don't know which one is signal in 6 wires of speedo meter. could you try to find a similar one like I posted in your S13 manual?
I assume your cluster use a meter control unit too like R34/S15. All signal to meters are control by it, so we need to power it and send signals from rev burner to it and let it drive the meters. I'm not sure connect wires to meter directly is safe.
In the pics I posted you should notice 4 connectors, (12) is ign(+12V) and 9 is earth(GND), (14) is speedo and (15) is rev counter, I can say just connect these 4 wire to make it work with S15 cluster.
Please try to find the same connectors in S13 manual, or try to send it to me to check.