[erimir]

Yes, it's too late to change the ballots, so the change would occur when the Electoral College votes. If the GOP somehow won, they would vote for someone else since Trump is dead, and presumably, the easiest choice to make would be Pence since he was actually elected. Selecting Ted Cruz or anyone else would be controversial, even given recent events.

Amusingly, I could see that scenario being a headache for Pence, given that Trump's electors are going to be full MAGA crazies who might vote for Trump even though he's dead, throwing the election to Congress. He'd probably still be elected in that scenario, but it would be amusing. As amusing as anything could be given the prospect of four more years of this GOP (even if under Pence which is not as scary as four more years of Trump).

Regarding Pence's election chances, it might be worth pointing out that Trump's White House has now been the setting of a superspreader event. Mike Pence was in charge of the Coronavirus Task Force. It's not a big jump from "you were in charge of addressing the pandemic" to "you let it infect and/or kill multiple members of your party, including the president". I don't think the particular circumstances of Pence ascending would be helpful to him (his best chances would've been associated with an assassination, particularly by a left-winger, followed by Trump dying of a normal health issue like a heart attack).