On Leto's request, here I am!
You already built a 64x64 lot, you want to place it in Sunset Valley, but there is no space, yes?
There is one simple solution, really. See those lots at the Pinochle area? There's a 50x50 somewhere in there, I believe. What you do is, you bulldoze that empty 50x50 lot, place a 64x64 in it's place (it fits just perfectly, and it's connected to the street), change the lot type to horse ranch or equestrian center (not quite sure what it is you've made), and place your lot down there.
This is similar to what I did in
Sunset Valley 5.0, and you can see exactly what I meant by checking the
map, more specifically for the Equestrian Center that I placed down. It's on the right side of the map. There was even enough space to spare to put a horse ranch next to it!
Hope this answered your question.