Thanks for the bigger pic on that Mirage document!
Like you said this document doesn't reference your VIN and the title has nothing to show it as a Mirage. Monzaaddict saw that the Mirage document shows Firethorn color vinyl bucket seats. Maybe if all the other options are on your car but over the years all those could be changed. Only 1,610 Monza's for 1977 had that RPO code UM2 (AM/FM radio tape player). Not that I can tell but it looks like it doesn't have the rear window defogger?
Maybe a Mirage but not the one the document shows, unless you have anything else it might take a resto package from VVS to be sure. Brian