They were available back in the day as a dealer installed option, generally made by Valley Industries. Vic Hickey also made them in the very early 70's.
To my knowledge, there are no currently manufactured swing out carriers that attach to a factory truck. That is, the ones I've seen go with an aftermarket bumper.
This is because the swing-out carriers have to attach to the sheetmetal, on the quarter above and below the tail light, and the tailgate. The good ones had a bent plate on the inside, to sandwich the quarter, but IIRC none of them sandwiched the tailgate. Since there's glass and stuff inside it'd be a tight fit. Even the weight of a 31" tire will eventually tear the sheetmetal. Been there, done that.
Should you want one, your best bet is likely Craigslist or your local equivalent. They show on Ebay now and again but can be expensive and a hassle to ship.
Or, as mentioned, you can go with an aftermarket bumper with a carrier. Might be a bit of overkill for a 33", but it's not gonna kill your sheetmetal.
For reference, some pix of the Valley Industries dealer type:
(The wrinkles at the top were not caused by the carrier.) I ended up welding studs all the way through the tailgate, since there's no window inside, so it's fairly solidly attached.
And the original use:
-- A