Looks like Inoki beat Spinks outright a decade later. Still, it's unclear if this second fight was fixed, given that it took place near the height of the Japanese bubble, and involved a loss by submission rather than a draw after significant injury on both sides. From the Wiki:
In 1986 Spinks would also fight and lose to Inoki in the eighth round of a match for the WWF World Martial Arts Heavyweight Championship.