I have the MTH gas station which uses the same type of car. I wanted to be able to change out the car and this is how I did mine.
Pick the car you would like to use. If it is one that has the pull back and run spring you must remove the spring assembly from the car for it to work. If it is a free wheeling car you are fine.
To modify the car to work:
Take a Popsicle stick and cut off the rounded end. It is the same size as the pin in the MTH product.
Coat the end of the stick with light OIL and let it soak into the stick wipe off any excess.
Wipe down the bottom of the car with Alcohol
Center the stick on the bottom of the car where the tab will be located. For better adhesion you could sand the area first. I did not do this with mine as it was a prototype test
Build up the area with UV activated glue/adhesive. After the fist layer the stick will stay in place. Continue in small layers until you reach the height and width required. Build it up higher than needed and trim down later. The UV glue will not stick to the oil on the Popsicle stick.
This has been working for over 6 months
When I first saw this UV adhesive I thought yea right this is BS. After using it now on many projects it now has a permanent place in the toolkit. It works as described and when exposed to the UV light cures in about 2 seconds.
This means do not use it near windows or anywhere that is exposed to Sunlight…..