The mod’s been floating about for years but only recently hit version 1.0. It started life as a makeover mod for the original Vice City, so in theory its a better version even before GTA V’s technobits. Here’s a trailer, which confusingly features remade cutscenes from Vice City’s singleplayer campaign that you can’t play with the mod - you only get to muck about with the map, and some homemade missions. GTA is obviously at its best when you’re just larking about with trucks and drawbridges, so I wouldn’t worry.
I say obviously, despite not having played any of Vice City. Six-year-old me was sadly deprived of gang violence. And these excellent fish.
The download page promises a “full port” of the original mod, plus modern enhancements I don’t understand but would gladly sign up for. MLO interiors. Instanced Grass. Pour it all over me. You’ll need to faff around a tad with other, supporting mods, and faff a tad further if you want the cars to be authentically 80s.