Problem to change COLLATE

Hi,

Is possible change default COLLATE/CTYPE to Portugese_Brazil.1252 ? I am using Centos6 with Postgres 9.1 in this installation of Postgres has only these locales installed.

pt_BR
pt_BR.iso88591
pt_BR.utf8
pt_PT
pt_PT@euro
pt_PT.iso88591
pt_PT.iso885915@euro
pt_PT.utf8

Are there some diference between Portugese_Brazil.1252 with others existent locales

Thanks.