Some SD40-2 units have undergone rebuild and some have not. The former Altoona Helpers are all across the NS system. I can tell you that 3337 a former Altoona helper is assigned to "C-Yard" in Morrisville and is used to shift intermodal buckets. A cab signal equipped unit is needed in Morrisville as the Morrisville Line requires Cab Signals. I can tell you that the 3337 has been put through hell. Many times it sounds like it's going to blow up.
Some of the High Hoods should also be retired. One of which I've been on had absolutely terrible Dynamic which was basically useless. Not to mention the thing couldn't get over 25.
Some High Hoods have also been equipped as Remote Control Locomotives or "RCL".