WF is also a 73 350. So you need the casting number to make sure. Hopefully it turns out to be a 67 400. I had an early 67 400 block that had the casting number near the distributor. Later 67 blocks and later years the casting number is wy back near the firewall on the passenger side. Tricky to get to but you can stick a camera back in there and see if you can get a photo.