The F intakes were supposed to be worth about 40 HP over the D intake from what I've heard. The Dove Tunnel wedge makes even more, but doesn't look correct and also has 4160 carb spacing, so you can't use the correct carbs or air bonnet.
Combustion chambers were usually around 72cc like the 427 low risers, the large chambers didn't come out until the medium risers. From what I've heard and read the heads, intakes, and different versions of the carbs were available over the counter until the early 70s, even listed in the 1968 Hi-Perf Parts Catalog.
My dad has a complete High Riser that was built by Carl Holbrook in 1978 and has been in a crate since. It had a 4v intake on it, but we picked up a 8v as its going in a T-Bolt clone as well. I've been able to trace the engine back through its previous owners and talked to the one who had it built. He as from Detroit and got the parts from friends at Ford. Everything looks like new, and being that they were later service heads they were probably less than 10 years old when they were built. We sold the 4v intake to a member here, and it looked like it had never been run. The original owner had it built for a Mach 1 drag car and then never finished it. The engine was sold with the car, and the next owner kept it as a spare! The best part was, he still had the original invoice from Holbrook Engineering, as well as 7 pages of Ford Blueprints for the heads and rocker assemblies.
We were planning on putting a HR in our 63 Galaxie as well, but decided to go with a 406 instead. The same member who bought the 4v intake bought our extra set of heads, intake, and rockers off of eBay tonight.