Even the 1932 census was heavily contested. In 1958, the Leftist pro-Palestinian camp was much weaker, but so were rightist militias compared to the 70s. However, the military itself was also weak. Syria had a different government.
I forgot where I got this from (but probably from the 70s), but this census could help explain the different attitudes of all the groups:
Conclusions (with generalizations):
Shia (at this point very much underpowered): Stronger central government (a government which doesn't just ignore them), in favor of stronger ties with Arab world and somewhat with Syria. No naturalization of the Palestinians, majority believes they should be deported.
Sunnis: Divided on government structure, in favor of very strong ties with the Arab world but not so much with Syria. Naturalization of the Palestinians.
Maronites and other Catholics: Federal government (to ensure own revenues), Catholics are less in favor of this (they live more dispersed), against ties with the Arab world, against stronger ties with Syria. 90-85 percent believe Palestinians should be deported.
Orthodox Christians: Stronger central government, stronger ties with the Arab world but not so much with Syria, Palestinians can stay as refugees only.
Armenians:: Centralized government, strong ties with the Arab world but not with Syria, Palestinians should be naturalized.
I'd think that the UAR would look at the civil war as an opportunity to expand its influence though and maybe it's borders. If that happens, we might have the six-day war in 1958 with Lebanon as the catalyst
Such a breach in balance would provoke an Israeli reaction, and I doubt the fresh UAR could afford that at this time.