Are all car stereo dimensions the same?

No they are not.

From the early days of motoring, on-board installations of radiOS were unique to that vehicle. Some mounted vertically, others horizontally, some mounted as an accessory under the dash.

In later years, towards the 50s, the faceplate and knobs appeared to be getting somewhat generalized, that is, they were becoming more and more familiar between makes of autos. For several years, a person could put radio a into car b, or any number of combinations. Then...you have the aftermarket units...apparently there were some makes that had the dimensions on the knobs a bit different, as they came with moveable shafts to fit different factory plates.

Later still, radiOS were designed by different makes again that made them unique, and not interchangeable. They now make kits to stick whatever radio you want into whatever vehiicle, with wiring harnesses that will mate said radio to the vehicle of your choice.

it's all confusing...give me a simple AM radio ANY day, I have an FM adapter that has an input for XM/Sirius, mp3, whatever I wanna listen to.