Research indicates that the father/son team that owned this car since 1967, modified it to emulate Maglioli's own 1968 racer and other Le Mans cars of the period.
When I discovered the car didn't have rear bumpers, I originally thought it was as a result of crash damage. But the body man said there was no evidence of a crash, and when I stumbled across pics of Duntov's famous white 1969 ZL1 "mule" I began to get a clue. But the street versions of the ZL1 and even the ZR1 just confused the issue.
Then more accidental discoveries led to the L88 Corvettes at Le Mans and Le Tour de France and the mystery was solved, at least for me. These FIA Group 4 cars consistently featured the same bodywork: front bumperettes delete, rear bumpers delete, ZL1 fender flares, wide American wheels, L88 hood, large chin spoiler, side exhaust, removable hardtop.
Here's a link that has many pics of Maglioli and his L88 car: https://www.c3registry.org/index.php?job=ShowCorvette&car_id=6074&uid=6616
And a few pics of my own car, as it looked when it landed in Melbourne, Australia (it's now in Sydney).
My current guess is that it was campaigned in SCCA Club Racing in B Production category, a class that no longer exists. That would perhaps explain why it was turned into a road car again, with the removal of the side exhaust, still with a lot missing (non-original seats, no headliner, homemade carpeting, no radio) but still with all its race parts (steel safety bellhousing, F41 suspension, ignition disconnect switch, Hurst). Even the front lower valance had been modified to accept an unusual chin spoiler of the era, which I was lucky enough to find again and install.
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1968E (2nd month production) convertible first registered California 1967 and a retired SCCA race car. It is still race prepped and built up as a '69 ZR1 (announced '69 but not built until '70); i.e., the L88 car with LT1 motor.