I have searched but cannot find it. Where would I find the lines to change to have USPS standard post show up as different wording? I found and changed fedex's already but cant find this one. I did see some interesting comments about USPS
Looking at the CLASSID values (dated July 2013), the response will include the phrase "1-Day", "2-Day", "3-Day", "Military", or "DPO" depending on the calculator's best guess at the average in-transit times based on the pickup and delivery post codes. The USPS also states there is no commitment to these in-transit times, other than Priority Mail Express.
So, there is probably nothing to update, and finding and killing those phrases should be easy. The code to add would be added near line 160