Take the gameconfig.xml from your downloaded "Best" folder (start with the 1x Traffic version for stability) and drop it into OpenIV.
Because modding sites change, here are the criteria for spotting the file: gta 5 gameconfig 103501 best
While modern GTA 5 versions have many creators, the legacy version 1.0.350.1 requires specific older files: Custom Legacy Configs Take the gameconfig
: It allows users to add hundreds of custom DLC vehicles and buildings (MLOs/YMAPs) without exceeding default engine constraints. gta 5 gameconfig 103501 best