Does anyone know how to do this?

I have 2-HR10-250's and one Sony Sat HD-200 that no longer can get HD programming.  I also have a 10 year old dish..3lnb oval.  In addition I have a very old but good Sony Sat-A2 and another Sony Sat-A65 in my home.  DirectTV has hosed my two Hr10-250's in the past couple of weeks with some update or another.  They want me to upgrade, but the tech people are clueless when I ask about diplexing my local off-air HD channels and the newer equipment.  They say that they don't have any off air tuners anymore and that I should just watch my locals in SD.  I told them to stuff it and have been looking for answers.

I have a Terk multiswitch that feeds all of my receivers now.  I have two RG-6 lines to each Hr10-250 and one line to the other locations.  I use diplexers to get my local off air HD channels now and it works fine.

How can I upgrade and still get my local off air HD stuff.  Tech support says there is no way to do it, but I don't think they are right.  There has to be someway to get it done.