Load Balanced Dual T1's - Same default gateway for both CSU/DSU's?

[Steven N. Fettig]

I know this is possible using a Cisco router with two or dual CSU/DSU's 
for data T1's, but I am struggling to figure out how to get this to work 
with FreeBSD: 
I have a Sangoma Dual T1 (CSU/DSU) card in a FreeBSD box I want to use 
as the router and firewall for.  Global Crossing has provided me with 
two T1's that they are "load balancing" on their end (they will not 
employ multilink ppp) - traffic will be distributed "evenly" across both 
T1's - one is not a main vs. backup - they are both mains and if one 
goes down, both go down.  I need to somehow tell the gateway/router to 
use two different pipes as the default gateway.  I.e. the far side of 
the wan is 123.1.1.161 for T1-1 and 123.1.2.166 for T1-2.  I can only 
add a default route for one and not set it to both.  Is there a way to 
either use ipfw or simple routing to make this work?  otherwise, I guess 
Cisco is it...

Thanks in advance,
Steve