Just think of it as handicapping. "Born to race, Bred to win" :-)

They weren't the only ones ineligible for Trans Am.

Remember, Production classes were for sports cars. Sedan classes were for
sedans.

Trans Am was a professional Sedan class.

It had nothing to do with discriminating against Corvette.

And the handicapping worked in Corvette's favor.  The Cobra was around
2000-2200 lbs with the 289 and about 2500 with the 427.  Corvette was about
3200 with the 327 and 3400 with the 427.  Tell me who would win?  Had the
equalizing rules not come into play, Cobras would have continued to run
Corvette from the race track, as while Chevrolet engineering wanted to build
a competitive race car (Grand Sport), GM management did not and would not.
So Corvette was only able to get marginally better with each change, and
could have never answered the challenge by Shelby.

Same with Porsche in the '70s.  They were restricted and weighted to
equalize them with others.  Look at any of Greenwood's race cars to see what
it took to beat the Porsches.  Do you think GM would have allowed something
like that as a Production car?

Showroom Stock as a class didn't appear until about 1970 for small sporty
sedans. Big bore cars were not allowed, being classes in existing Production
classes.  The idea was that Showroom Stock was just that, right off the
showroom, with very little race-prep, such as a BOLT-IN roll bar, fire
extinguisher, and seat harness.  These items were safe enough in a small
slow car and marginally unsafe in a car as fast as a Camaro or Corvette. The
reason big bore cars were not in Showroom Stock was due to safety.

For some reason I an unaware of, SCCA decided to bring in a Showroom stock
class for big bore cars in the early '80s.  Possibly it was because there
were no big bore Production classes anymore, since A-Prod, B-Prod, A-Sedan,
etc. and become GT categories such as GT-1, GT2, etc. and allowed very
non-production changes like Wilwood brakes, tube chassis, fiberglass body
panels (for metal cars), and so on.

What really ruined Corvettes in racing was MONEY.  In the early '60s, you
took your stock Corvette, put in a roll bar, changed tires and raced, much
like many do with autocross today.  Soon it became more modifications, until
the car was no longer street legal.  This dictated more money as it was no
longer race on Sunday, drive to work on Monday. As the modifications became
more and more, the expensive went higher and higher.  Soon it was cheaper to
buy a brand new Corvette than to race an old Corvette.

Today, how many of you have $1000 to $2000 to spend on a weekend?  Every
month? With zero return but a trophy?  After an initial investment of
$40,000 to $75,000 (in cash, not a car loan).

And if you want to get somewhere productive, make that weekend expense about
$4000 to $5000.