I believe it is possible to integrate H323, SIP and SCCP on one network. The 1760 can support H323 and SIP. However, it does not support SCCP, but it doesn't need to. SCCP is mostly used between an IP Phone and the CallManager.
What you will need to do is configure the IP Phones and CallManager. Then configure the 1760 as an H323 gateway in CallManager. You can then also configure SIP on the 1760 and configure it with your SIP Proxy Server or other SIP components.
You'll need to configure the dial-plan on the 1760 to route calls to the appropriate system, CallManager, SIP, etc.
Not sure whats going on with your out bound calls, I'd need more information in order to make any suggestions. Take a look at this link for some info on configuring gateways with CallManager.
Just a note, the c1760 can support SCCP in two ways:
1. ITS (sorry, Cisco Marketing -- I am actively refusing to use the "CallManager Express" moniker), where you would manually configure ephone's and ephone-dn's, and "off-net" calls get routed via dial-peers.
2. SRST, which is not what the original post is really looking for, but gives the IP phones a place to register when the lose their primary call control agent (typically a CallManager, although it is my understanding there is an SRST/SIP now).
Both of these technologies are in the c1760, and both use SCCP to control the phones. ITS 3.0 is available in 12.2(15)ZJ -- but older versions date back to early 12.2T and many BU specials.
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