how to make pfsense work as multiple proxy server

[tcpzix]

hi
my pfsense work as non-transparent proxy in the lan network for accessing internet with port 9050. i want to know if i have proxy server in the internet network how i can make pfsense to pass the client internet via my private proxy server just with changing port in the client side? something like this:

host<>192.168.1.50:9050(pfsense)<>google.com
host<>192.168.1.50:9060(pfsense)<>proxy1<>google.com
host<>192.168.1.50:9070(pfsense)<>proxy2<>google.com

and also can i use proxychans in pfsense?