The Hot Wheels Emergency Squad and Ranger Rig, both released in 1975, were the same casting with different paint and decoration. In fact, several models released in 1975 (Backwoods Bomb, Paramedic/Super Van, Emergency Squad/Ranger Rig, Ramblin’ Wrecker) used the same molded base and grille.
Emergency Squad is said to be based on the TV show Emergency! which ran from 1972 until 1977 and was one of my favorites. The vehicle in the show, Squad 51, was a Dodge D-300 and it now sits in the Los Angeles County Fire Museum along with its co-star, Engine 51.
This redline-wearing first release from 1975 came from eBay. I also still have the 1977 blackwall version of Emergency Squad from my childhood.
Hot Wheels | 1975 | 7650 | Emergency Squad | red with white & yellow trim, blue plastic insert | HK | rl
Next up is the redline 1975 first release of Ranger Rig.
Hot Wheels | 1975 | 7666 | Ranger Rig | green, red plastic insert, Forest Service Unit 71, etc. | HK | rl
In 1986, the casting was renamed Rescue Ranger (and more recently, HW Rapid Responder) and many, many variations followed. This green version with a yellow insert and colorful Forest Service emblem on the doors is from 1986.
Hot Wheels | 1986 | 2537 | Rescue Ranger | green, yellow plastic insert, Forest Service Tools Seeds | MY | bw
Finally, this red model with yellow insert and Hot Wheels Rescue Unit on the doors is from the 1988 Workhorses Series.
I also have a yellow Airship Support Team version from the 1994 Blimp & Support Team 5-Pack.
Hot Wheels | 1988 Workhorses | 5145 | Rescue Ranger | red with yellow plastic insert, yellow and black Hot Wheels Rescue Unit | MY | bw