Wow! 1/24th scale? Can you even GET 1/24 scale slot cars any more? A 4 lane would have to be what, about 18" to 20" wide, and more on the corners? I had a 1/32nd scale once, and we had a ball with them after we re-wound the transformers for more secondary turns with one dedicated to each lane.... That ended the strategy of letting off of your controller just as the other guy got into a hard turn, giving him all the power

The old Lionel's are 027 and O gauge track, which works out to 1:48 scale. That means your slot cars will be twice the size, in proportion, of the train. About the closest you'll come to matching them up is with HO gauge train and the matchbox size 1:64 slot cars, from my memory. Charlie's a big train guy, maybe he can help with up to date info.