The older cars in the game, when equipped with automatics, seem to take just about forever to kick down when you hit the gas. Maybe some old automatics actually behave this way, but definitely none of the ones I've experienced. Here's a '63 galaxie getting the gas pedal shoved into the floor and doing a 3-1 kickdown. Just for reference.
i've noticed this only on the 2-speed automatic gearboxes in the bluebuck, the burnside and the miramar. the 3-speed autmatic burnsides, bluebucks and moonhawks seem a bit lazy but they downshift fine.