SAP Gateway core components version compatibility

Hello Gateway/MCF Guru,

We are in the planning stage of installing SAP 1.2 SP5 on ECC 6.0 EHP7 NW 7.40 and CRM 7.0 EHP3. Since both system has different version of NW stack, the gateway core components and backend requirement are also different. Based on the version and the scenario below, does that work? or we have to upgrade CRM to be compatible? Or does not matter what NW version we are running on?

Here is what we have:

1) Gateway server

IW_FND and GW_CORE 200 SP11

2) ECC 6.0 EHP7 NW 7.40 (SAP_GWFND)

3) CRM 7.0 EHP3 NW 7.0 (IW_BEP)

Thanks