If you want add-on vehicles or peds and your game is crashing, you should install a game configuration file and its requirements to prevent it from happening.
Heap Limit Adjuster: https://www.gta5-mods.com/tools/heap-limit-adjuster-600-mb-of-heap
and Packfile Limit Adjuster: https://www.gta5-mods.com/tools/packfile-limit-adjuster
When you install the gameconfig, I recommend using the "1x traffic 1xpeds (Means Gta base)" gameconfig file.
(OpenIV) Install to :Mods/Update/update.rpf/common/data/and replace gameconfig
(The file may be outdated depending on what version you have) if you have the newest version of gta5, you MAY need to wait for an updated version.
Install Packfile Limit Adjuster and Heap Limit Adjuster to your gta directory!
Hope this resolves your crashing problem,