What I meant when answering the initial question was , if I send a text from the Gvoice app (or the GV web portal), the text shows up (to the person I send it to) as being from from my Gvoice number, 422-1234.
If I send a text from GoSMS, it shows up (to the person I send it to) as being from my VM #, 587-1234.
I do not know a way, and I do not think it is possible, to send a text from GoSMS that shows up (to the person I send it to) using GV, as being from 422-1234.
When I set up GoSMS initially it did not ask me which service I want to use to send texts, GV or VM. Possibly if you set up your phone to only use GV it's possible?