Which year 280z S30 would you recommend?

I don't believe that is correct. The cats were only standard on California cars. I have owned 2 '78 cars - one federal and one CA. The federal car did not have a cat. And it wasn't just removed, since the floor sensor and warning light system were not there either (That car is now in boxes in my garage - so I got a lot of experience on what it did and didnt' have). My current '78 daily driver is a CA car, and DOES have a cat. One other point is that both of these cars had manufacturing dates of 5/78, and VIN numbers that were only 4000 apart.

Ahh okay...

My '76 doesn't have a cat, and I was told that domestic cars started requiring cats in '74... I assumed that Nissan picked up on that trend following the 1977 minor Z-redesign. My bad then.

... Looking forward to those pics Dogma!