The original download links from 2014-2016 are long dead. However, the SLRR community remains active on Discord and the Redline Zone (redlinezone.com). Search their “Mod Archives” section for:
HD skyboxes, semi-transparent UI elements, and expanded paint palette The original download links from 2014-2016 are long dead
Street Legal Racing: Redline 2.2.1 MWM by Jack V2 Pre-Release 4: The Definitive Guide semi-transparent UI elements