I've got a Telus hero too. Telus Heroes were released with the latest Telus specific ROM version on them. They had no updates, so there was no way to get the original firmware file for the Telus rom. Best you can do is install the latest generic HTC ROM, which is basically the same thing. [ROM] Official HTC Hero RUU ROM + Radio Links - xda-developers
On that page, it would be the 2.73.405.66_WWE one.