Looks good, but readme file is completely useless.
Install guide:
Go to folder mysummercar_Data and rename file sharedassets1.assets to sharedassets1.assets.backup
Use Unity Assets Bundle Extractor. Select File -> Open -> sharedassets1.assets.backup
Find the name datsun_hood using the program's search feature, click import raw, and select the datsun_hood.dat from downloaded archive.
Save file as sharedassets1.assets
Don't forget to delete the file meshsave.txt from your save.