There are grove marks for four cars and the width of the grove marks does work with other types of cars, however I will say matchbox cars may not work the best due to the depth of the groves. It does work with Thomas trains, my son has used it for hot wheels trucks, he has tried with cars and it works but not AS well as a vehicle that has a higher underside clearance.
I doubt if it weighs more then a lb or two. My 20 month old grandson loves it. The car carrier disconnects from the truck and I taught him how to reattach it. He learned hand to eye co-ordination with this toy.