I've got a set of 197 heads and a 1971 455 HO intake manifold that I'd like to "trade" for a set of 7F6 heads and intake, so I've been looking.
On the other hand, the 455 HO is essentially a 455 CID Ram Air IV that you can run on pump regular and build to put out 500 HP and 600 ft. lbs without breaking a sweat. 
Interesting you bring that up. I remember people calling 71 455 HO heads, "197"s, as compared to 191s. It's been a while since I looked, but I think the last digit resembles either or, the way it was cast. Guess it depends on what school we went to
As for the RAIV comparison to the 455 HO, the only thing similar is the exhaust ports, (round) and exhaust manifolds. I'm not sure about the aluminum intake, or tall intake ports. The HO doesn't have the good 041 cam, the long tulip valves or heavy valve springs, or the 1.65 rockers. But what the HO gives away on the top end, it does make up for it on the bottom and middle RPM range.
It's more than the shape of the exhaust ports and exhaust manifolds - the heads are the same except for the size of the combustion chambers. The 455 HO has the same size and basic shape intake and exhaust ports (the roof of the '72 intake ports is slightly different than the '71) and uses essentially the same aluminum intake manifold and cast-iron cross-over as the RAIV (different part number, same shape); it also has 4-bolt mains, as did the RAIV. Rocky Rotella described the 455 HO in one of his articles as follows: ". . . GM mandated a maximum compression ratio of 8.5:1 for the 1971 model year. Pontiac responded by essentially increasing the displacement of its otherwise high-compression 1970 Ram Air IV to create the 1971 455 H.O. "
https://www.motortrend.com/how-to/mildly-modifying-pontiacs-455-h-o-add-nearly-100-hp-factory-gross-rating/The RAIV was a higher-revving engine than the 455 HO. It made its peak HP 800 RPM higher than the 455 HO, and it's torque peak occurred 300 rpm higher, and was 35 ft lbs less. Perhaps that explains the higher-ratio rockers and tuliped valves, as they would mostly make a difference at a higher RPM.
455 HO
HP 335 @ 4800 rpm
TQ 480 ft·lb @3600 rpm
RAIV
HP 370 @ 5600 rpm
TQ 445 lb-ft @ 3900 rpm.
But anyway, at worst, the '71-72 455 HO was a detuned version of the RAIV - same basic engine, with a milder cam and associated changes (valves and rockers). That could be because, while the RAIV was always an optional engine in the 1969 and 1970 Trans Am, EVERY Trans Am in 1971 and 1972 got a 455 HO. Maybe Pontiac figured that not everybody would be willing to live with an engine with the RAIV's characteristics if they didn't have a choice. And of course, then, as now, if you WANT a 455 HO with tuliped valves, 1.65 ratio rockers and an 041 cam instead of an 068, that could be arranged.
I've seen $4500 as an asking price for 455 HO heads, but I've also seen $2500 recently. They aren't cheap, they aren't as expensive as RAIV heads.
I've seen some references to the '71 heads as 191 heads, or even 197 / 191 heads, although I think that it's supposed to be 197. The appearance of the cast numbers vary, and on some the "1" and the "7" resemble each other more than others, but most that I've seen, including mine, look like 197. If anything, some of them look like "797".
