This is a good topic.
I would want to find a DZ block to at least say the car had one. Finding one as close to the build date of your car to me is just the thrill of the hunt for the original. Mine is gone, so I found one that is extremely close and have it sitting, all together and ready for me to get off my lazy ass to install it. Well, that's not entirely true, I'm not lazy, but I keep looking for my original in the hopes that if I ever do stumble across it I have something I can make the switch with. I don't ever think it will happen, but, you never know. I bought my block cheap around 2002, but today with the blocks/parts being held hostage for a hefty ransom, which to me really stinks, I'm ahead of the game money wise.
On the Camaro that is a Z28 or not a Z28 without the engine, IDK. There's a lot of people who think a lot of different ways and have a lot of different views. For me the Z was built a certain way, not the same as the plane jane Camaros or the SS Camaros. I'm in the middle on that I think. If you lost the engine and had to put in another to drive it, be it another 302 or 350 or a straight six, isn't it still a Z28? From day one when that first piece of metal was spot welded to the next piece of metal and so on that car was destined to be a Z28. Some people think it's the engine that makes the Z28, of course it does, but what about all the other Z28 specific parts that made it a Z28? This is a subject that will be debated on as long as there are people on this earth to debate with.