Does it wander, or are you over correcting it?
I believe the pump pressure the G3 Hemi puts out is quite a bit higher the the pressure the old pump put out. That would create a very sensitive steering and over correction might make it seem like it was wandering. My son ran into this when he installed a 5,7 into his 57 Wagon, but I don't remember what we did.
There are a few options for reducing the pressure output of the steering pump. Google is your friend on this one. Gene