I can verify that there was an actual ZL1-based 454 test/development engine stored by Chevrolet Engineering for decades at Milford Proving Ground. When I first viewed it, the engine was in a disassembled state and was kept in a custom wheeled, varnished wood crate. There were retaining spaces for all components down to the individual valves, lifters, pistons, etc. The crank was held by a cradle integral to the interior of the crate. The crate exterior had information indicating that the engine had been shipped to Diamond Engineering out of the Detroit area at one point. The block and heads were aluminum with corresponding Winters Foundry casting marks. This engine was secreted away along with several other high performance small blocks and an L72 big block in an area away from prying eyes. The fellow who oversaw the storage area showed me these engines early on in my tenure as he knew of my interest in such things with the agreement that I "forgot" what I had seen. Eventually, an enterprising co-worker who also knew of the engine(by being buddies with the storage guru), decided it would make an interesting development study by installing it in a C1500 pickup. He got permission from the storage guru to temporarily use it and the install occurred on a weekend during off shifts. I had an opportunity to drive this combination on the road system including the North/South straight with my co-worker riding shotgun. It was an animal. I can only imagine what it would have been like in a lighter platform. There is a possibility that this was the same engine described in the account of the Corvette mentioned previously.
