1- INSTAL ALL THESE MODS 

-Manual Transmission
https://pt.gta5-mods.com/scripts/manual-transmission-ikt

-Custom Gear Ratios ( for realistic gears )
https://pt.gta5-mods.com/scripts/custom-gear-ratios

-Dial Accuracy Fix ( To correct dial on some cars )
https://pt.gta5-mods.com/scripts/dial-accuracy-fix

-Custom Torque Map ( Realistic torque and HP )
https://pt.gta5-mods.com/scripts/custom-torque-map

2- After all mods installed, You open GTAV folder with come this archive, copy all folders inside and drop on your GTA5 base folder.

3- Inside the handling.meta folder you will see folders separate by Manufactures and cars, there is a link of car and maybe a soundmod of them.

To install the handling USE OPEN IV. go to GTAV/Mods/Update/x64/dlcpacks and select the car that you have installed. 

always the handling.meta file will be on dlc.rpf/data/ inside the folder of your car mod, just replace it. 

3- Done. When you enter in the game, the .ini and .xml files of others mods will be load automatically. :)