Thanks for the URL fix.
This is true, you'll need the different actuator and you may be satisfied with the results. The problem is the dead zones. Sure, you could bend the leafs to try to minimize the dead zones, but since your looking to change a 8 way to a 4 way I'm willing to bet you won't be happy unless you swap out the base and have a physically restricted 4 way.
Since your going to need the actuator anyways - you might as well try it with just the actuator and then look for a base. I found a replacement actuator at Home Depot.