Rokuro's brother, Naya Goro, Dai Shuryo aka the Great Leader from the Showa era Kamen Rider series, plays Goemon [pilot only] and Inspector Zenigata in Lupin the 3rd. Rokuro also dubbed Hongo Takeshi in the Kamen Rider eps that were shot after Fujioka had his stunt accident. I think he dubbed eps 9 through 13.
That would be correct. Takeshi Hongou, out of costume, had to be used sparingly (especially by recycling unused footage of him from previous episodes).
Gorou Naya was also the Japanese dubbing voice for Nick Adams, especially in the Toho-produced films
Frankenstein Conquers the World,
Monster Zero, and
The Killing Bottle. He also dubbed Joseph Cotten in
Latitude Zero.
Gorou Mutsumi, best known as SAF Commander Umino in
Fireman, alien leader Kuronuma in
Godzilla Vs. Mechagodzilla, the similar alien leader Mugal in
Terror of Mechagodzilla, and the lead villain in
Cybercop, was the dubbing actor for Russ Tamblyn in
War of the Gargantuas.
Masaki Kyomoto was the voice of Dore Krause's "Jack Shindo" character in the Japanese dub of
Ultraman: Towards the Future. In that dub, Hiroshi Fujioka was the narrator, and Akiji Kobayashi was the voice of Ralph Cotterill's "Colonel Arthur Grant" character!