Eeeeeeeeeeeeeyeah sort of.
GM proper never offered them from the factory; they were a dealer item.
I believe they were generally the Valley Industries brand, though some may have been Hickey.
Further, I know these were offered in the '70's:
1975
1976
etc. Those are the Valley style. The Hickey one is this one:
http://brochures.slosh.com/1978/blazer2.jpg
on the brown rig in the back.
Here they explicitly state it's a dealer thing:
http://brochures.slosh.com/1979/blazer7.jpg
ANYWAY, point being that GM seems to have stopped listing them ca. 1981, but the tailgate and sheetmetal are the same for 73-91, so you can use an earlier one, should you so desire.
(NB: The General occasionally offered these on Suburbans, too, including the Ducks Unlimited and Outdoorsman editions.)
Of further note is that the body-mounted carriers are only good for stock sized tires; even a 33 x 12.50 WILL tear your sheetmetal eventually. Been there, done that, got the T-shirt... so this whole issue may be moot, if you're thinking about big tires.
-- A