I also am a big fan of the HS cars, (the H is a Vega, the HS is the rest, S is for "Special") The cars were designed to be used with a rotary/wankel engine, but the emissions issues killed that.
My dad bought a White 1980 Sunbird Notchback new in Feb 1981, only option was power brakes. 4sp, AM, manual steering, tan vinyl seats. As it rusted over the years, he picked up a 1977 IMSA Spyder with a 305 (the body panels were already gone) and we planned to use that for parts on the Sunbird. We also got some parts from a 1978 Sunbird, mainly the tilt column.
The last one we had was a 1980 Monza Notchback that was Red with Black cloth interior. We got it in the 1990s with only 19K miles on it. When we were done with it, it had factory gauges from the spyder with working clock & tach. PS,PB, Tilt, Auto, Rear sway bar from a Spyder, front bar was Pontiac Performance "Formula Sunbird" over the counter (I forget how big, but it was huge and heavy) We ended up putting a rebuilt 327 from our 1967 El Camino in it with all of the factory mounts/accessories/manifolds from a 1977 IMSA Spyder. The hood was louvered and slotted in the front like a mini scoop, very sharp car, and fun to tool around in. I can't find any pictures of it, but there might be one around somewhere.