Donald J. Trump (DJT) received roughly 63 million votes in 2016. Geroge W. Bush (GWB) received 62 million votes in 2004. At the same time the US Population has grown from 293 to 322 million people (not necessary the population eligible to vote). On a map the coalitions look similar, also the demographic composition looks similar (see (ropercenter.cornell) and here (Pew)).
Also, I'd like to exclude everyone who is younger than 30 in 2016 (the voting age is 18, everyone who is younger than 30 couldn't vote in 2004). People who are dead in 2016 but voted for GWB, are excluded by the scope of this question, because I'm only interested in one direction: DJT's voter who voted for GWB; not GWB's voter who voted for DJT.
So the question is: given a DJT's voter in 2016, what is the probability that they voted for GWB in 2004 (based on polling, statistics, voting registers, ...)?
A starting point is this analysis between Barack Obama and DJT (Rasmussen). The bottom line is, that Barack Obama received a lot of votes and roughly 10% voted for DJT, but "it would not be surprising if Obama’s percentage were somewhat inflated and Romney’s a bit diminished". Is there a similar analysis between DJT and GWB?