Child safety seats for our cars?

I now need to take the grandchildren to car shows. The seat belts work for the infant base but I think they are going to be to short for the toddler seat. On all of our new cars they have those handy little rings that you can just clip the seat base into. Anyone have any info or ideas on how to make something like that for our old cars?

 

Have you thought about a seatbelt extender? Something like this ?

 

I have a 2 & 5-year-old and I've used both of their full size seats in the backseat of the '66 GTO, '67 GS400, or '72 Skylark. My '72 Skylark has the factory locking lap belts in the backseat that reel-out and they are also longer than the older cars. For the '66 & '67 the belts are barely long enough, but they do work even without an extender. If your front belts are longer, it is allowable to put them in the front seat since our cars don't have airbags although I always prefer to use the rear.