Most Helpful Girl
I believe it is "What he said is right"?1
Most Helpful Guy
I think in most cases "is right" is right.
If what he said is no longer right but was right at the time he said it, then "was right" would be right.
Also, I think in storytelling or writing, you can say "was right" to provoke certain emotions.
For instance, if someone in a story said "Lucy is dead," then someone responds "No way, I don't beleive you," the narrator could then state: what he said was right. Lucy is dead.
I am unsure as to the grammatical rule behind that logic though... I just think it works, I may be wrong.1