You gotta set up a dead man's switch (not literal give the evidence to a lawyer or do a deposition or whatever). Do that before you blow the whistle and announce that at the same time.
A dead man's switch is better if you never intend to release that info otherwise (using it as protection) or you just want revenge from beyond the grave. The company would have to know you have a dead man's switch in the first place to be deterred and might think they can stop or better discredit the information with you dead even if they do know.
If you're a whistle blower that's going to be part of a court case, that information is being released either way so it's best just to dump it on the record under oath in a deposition asap.