asterisk users - Jan 2004 - Bridging ethernet over hdlc

I'm attempting to bridge ethernet over hdlc between two * boxes.  If anyone
has any information they can offer concerning this, it would be greatly
appreciated.

Here's the configuration the companies IT guy wants to bridge.  I have it
working already without a bridge, but he wants the head box's ethernet to be
on the same subnet as the ethernet across the span.

Pardon my horrible representation:

main network ------>eth([head box] .10.0)--- hdlc([span between
buildings])----T1----hdlc([span between buildings])--eth([head box]
.10.0)--<--subnet

Google searches aren't turning up much for me.

Here are two resources Mark found, but I can't see the application and one
of them looks like it is not free.

http://sweb.cz/Frantisek.Rysanek/sync/dscc4+HDLC-Mini-HOWTO.html

http://www.etinc.com/index.php?page=etutils.htm  <= not free

Thanks,
Christian