I don't think you can do it with that hardware. A PLC-5 may have a channel configured as a RIO adapter in order to share information with a scanner from a different PLC.
For two SLCs, you could use the 1747-SN in one of them and the 1747-DCM in the other. We have a PLC-5 that communicates over blue hose to 4 SLCs each with a DCM module.