The oldest thing my local volunteer department had in service up until a few years ago was a 1950 military surplus dodge brush truck, it was in service with the department up until 2020. I could see alot of volunteer companies keeping trucks that old and small around for brush fires.
I have not tried dispatching the private ambulances on standby or patrol, but it'll still purchase another ambulance even if you have none of the original four deployed on the map.
That's why I put it as a suggestion. More of a temporary model. Could also be a prototype in that era. But whatever. Author's choice
As for the private ambulance have you tried putting them on standby? Or does the dispatcher just do the same thing?
I Have A Idea To Add More Weapon To The LA Mod Like Giving Police Officer AR-15 Or Shotgun And Bulletproof Vest Same With The CHP And The LASD, LAPD SWAT Also Add Riot Equipment Like Riot Shields Tear Gas Grenade Launcher And Last Thing Is Add A New Unit The US Army Tank Like The M1A1 Abrams