King Kong vs. Godzilla’s Japanese cut has three principle sound mixes:
1962 Magnetic 4.0 Stereo. (Directional dialogue. Used for the R2 DVD)
1962 Academy Mono. (Uses the alternate mono recording of the score. Other differences unknown to most)
1991 Stereo. (Centered dialogue. Also used for the 2008 HV broadcast)
As far as I know, the 1962 mono mix has been restricted to early LaserDisc and tape releases (from '86 and '89) and it is not present on the 2001 R2 DVD. I believe the 1970/77 re-cuts also use the same mono mix stems. Here is a video in all probability sourced from the 1989 master, as it features a pristine TohoScope logo and has the more prominent native vocals heard in the mono score.
This site (in Japanese) has some interesting information pertaining to the film’s presentation on home video during the 80s and 90s. If anyone is willing to obtain either one of first two LDs listed, a simple preservation would be instrumental to those curious about the mono presentation, myself included.