“The 88 Callaway ZR1? Never existed.”
supercars.net
1988 Callaway Sledgehammer Corvette
This Sledgehammer reached 254.76 mph at the Transportation Research Center (TRC) in Ohio and became the world’s fastest street-legal car for some time.
It was built up by Reeves Callaway in Connecticut as an example of what was possible with the new ZR1 and and turbocharging its LT5 engine.
Supercars.net is a bit mistaken there. Again. They’re pretty inaccurate.
https://www.mecum.com/lots/FL0114-173940/1988-chevrolet-corvette-callaway-sledgehammer/
That’s not a ZR1.
The ZR1 would not appear until the 90 model year and the engine is completely different looking - the 32V heads necessitate a different intake, etc.:
https://www.caranddriver.com/reviews/a15141952/1990-chevrolet-corvette-zr-1-archived-test-review/
You are conflating the two cars.