UpdatedSCM is an SCM mod for GTA: Vice City to enhance the gameplay a bit, while also fixing little bugs. It has things like MC Tommy, some beta cell phone conversations, more ped variety in certain missions, mission corrections, improved 'Supply & Demand' mission, skippable intro help messages, skippable phone calls...
(Yes, this includes everything now.)
...And check out its changelog to get more idea about what it does.
Besides the main variation's SCM, there are also two other SCMs, depending on your need:
- Save-Friendly SCM: this has most of the changes from the main variation up until a certain point that does not necessitate a new game. (The changes you do not see here compared with the main edition are all those which require a new game and thus would crash the game while trying to load it.) So you can use this with your old saved files. (Still: be cautious and beware that your save files might become corrupted if you overwrite them, so at least save in a different slot or backup your save files if you use a new SCM.)
- Without MC Tommy SCM: the only difference between the main variation and this one is that this does not contain the MC Tommy model addition.
Only the latest version's changelog is included here (which applies to both the "main variation SCM" and "without the MC Tommy SCM" file - the save friendly SCM's changelog is in the download):