Get a VK56 engine from a Nissan Titan and drop it in there
You might be able to find a used VQ on here or eBay.
Is it worth it? My guess would be no. But you don't know until you get the numbers together.
Unless you are planning to drive the car into the ground after you get it fixed or just have a connection with it and really want to fix it, I would probably be looking at another car even if I still wanted another Z.