I got this from Rich Fields @ CRG when I asked the question.
The heater delete option was not allowed under US law as of
1 Jan 1968 because a new Federal law took effect on that
date (see below) mandating a front window defroster (and
thus the heater was required). The heater delete is listed
in the 1968 assembly manual, and might theoretically have
been briefly available at model introduction in September
1967 through the end of the calendar year; however we have
never seen a documented 1968 Camaro with a heater delete,
and Chevrolet production records show none as being sold.
Heater delete plates continued to be made for
over-the-counter sale after 1967, and can and were applied
to 1968-69 Camaros as an after-factory modification.
However, after 1967, heater delete plates were only used by
the factory on export vehicles or vehicles assembled
overseas, such as the Yutivo Phillipine Camaros.
For reference, see:
http://www.nhtsa.dot.gov/cars/rules/...s/safstan2.htm
Standard No. 103 -- Windshield Defrosting and Defogging
Systems -- Passenger Cars, Multipurpose Passenger Vehicles,
Trucks, and Buses (Effective 1-1-68)
This standard specifies requirements for windshield
defrosting and defogging systems.
Best wishes,
Rich Fields
Camaro Research Group
question on heater delete cars.