The two Christian parties were strong in Eastern Indonesia, but Muslim parties also had a significant following. The PSI was a political force only in Bali. Map shows parties winning 5% or more of the vote, by province.
Feith, Herbert, The decline of constitutional democracy in Indonesia. Ithaca NY: Cornell University Press, 1962
Herbert Feith, The Indonesian elections of 1955. Ithaca, NY: Cornell University Modern Indonesia Project, 1957.