I just switched from Comcast to Fios yesterday. My new Fios Cisco 435HDC box used the exact same codes as my old Comcast DCT 3416 box, no change to the remote required at all!

Took me a few hours to figure that out as it never occurred to me that the old codes would still work, it was only when I accidentally tried to change the channel using my old remote, out of habit, that I realized this :)

So try the Motorola STB codes on the 435HDC. Not sure if you'll find the 3416 or not, but I think many of the Motorolas use the exact same codes.