For proper functionality, the engine pack must be placed below truck mods in the game's Mod Manager list.
3406 A/B/C Mechanical, 3406E, 3408 TTA, and C15 (including a Straight Pipe version).
In-game, these engines typically appear in the garage search at a price range around $26,000 (though some variants like Volvo D-series may appear near $8,400 ).
To achieve the best audio results, it is recommended to turn off cabin reverberation in the game's sound settings.