Installation:

1) Install revp50demo folder to: Grand Theft Auto V\mods\update\x64\dlcpacks
2) Install into Grand Theft Auto V\mods\update\update.rpf\common\data\dlclist.xml this line:
<Item>dlcpacks:/revp50demo/</Item>
at the end of list, but before of </Paths>
-- Optional--
3) Install Classic Car Colours mod by GreenAid - https://www.gta5-mods.com/misc/classic-car-colours-greenaid
4) Replace carvariations.meta in Grand Theft Auto V\mods\update\x64\dlcpacks\revp50demo\dlc.rpf\data

Added vehicles list:

Los Santos Police Department Units:

ist57pol - BMW Isetta '57

Los Santos County Sheriff Department Units:

ist57srf - BMW Isetta '57

Blaine County Sheriff Department Units:

ist57bsrf - BMW Isetta '57

Contacts:

Email: johnlozano228@gmail.com
Blog: https://blogger-lozano71.blogspot.com/
YouTube: https://www.youtube.com/channel/UCVONyOcHe63HRgv0webZEMQ
Boosty: https://boosty.to/lozanosworkshop/donate 
Discord: https://discord.gg/pfdT4nR
PayPal (inactive): https://www.paypal.me/Lozano71

Credits:

Emergency lights:

Most of emergency lights and equipment 3D Models: solo, Lundy, 11john11

Winchester M1912: - Morrice, toitoine66

Overhauling of emergency lights, creation of carcols.meta and radical edits of 3D Models: Lozano71

All liveries and assembling of pack: Lozano71

BMW Isetta 300 '57

Model: Forza Horizon 3 & Motorsport 4 
Convert: baba0rum
Upload: LeeDaeul
Template and fixes: Lundy
Fixes and finalising: Lozano71

Credits list may lack some nicknames, so, If I missed someone, or you see errors in credits, please note me about that, I’ll be happy to fix that, because my work was impossible without these authors.