Rockefeller was considered a liberal. Baker was a moderate. (BTW, Ford didn't dump Rocky, Rocky left on his own in November 1975 to keep the party united, Ford just accepted it. Reagan didn't announce his run until after Rocky withdrew. It's not appropriate to compare Rocky vs Baker, as it would not have been such a comparison at the convention). So I don't think he would turn off the Reaganites as Rocky would. Furthermore, if Reagan wanted to be well positioned to be the GOP nominee in 1980 (and he was getting older so he couldn't afford to wait past that), he'd have to back the ticket strongly. He had already risked splitting the party too much. Reagan himself had promised to make liberal Richard Schweiker as his VP in a failed attempt to woo moderates to become the nominee.
Since it was assumed Baker was going to be the VP pick right before Ford asked Dole, I don't think it's that much of a stretch if he went along with it. It might not galvanize Reagan's conservative base as much as Dole did, but it would have more appeal to the center.
Baker's big plus is that he would not have made a "Democratic wars" gaffe that cost Dole a lot. But Ford needed someone to really fight as he planned on taking a more statesmanlike approach - would Baker have done it? Baker would also help Ford on the Nixon pardon issue as it was he who asked "What did the President know and when did he know it?" to John Dean. It would promote Ford's image as an honest man.
The real question is would Baker be able to push Ford ahead? Let's look at the closest states that Ford lost in 1976.
Ford lost by 240 to 297 Electoral Votes (EV). He needs 270 to win. He needs to switch 30 to win.
Ohio (25 EV) was closest - only 0.27% difference or 11,116 votes.
Wisconsin (11 EV) is next. 1.68% or 35,248.
Other possibilities to switch are:
Mississippi (7 EV). 1.68% or 14,463.
Hawaii (4 EV). 2.53% or 7,372.
Other than perhaps Mississippi, the potential conservative votes lost probably don't equal the moderate votes won. And it's possible Baker from TN might appeal to southerners in MS.
If we look at Ford's closest victories to see if they might switch to Carter, we're also not seeing states where conservatives likely hold the balance.
Oregon (6) 0.17% or 1713 votes.
Maine (4) 0.84% or 4041 votes.
Iowa (8) 1.01 % or 12,932.
Ford has a lot more close wins than Carter and seems vulnerable, but they are very conservative states. Appealing to moderates probably boosts his totals there.
I think there is strong, but not conclusive, evidence a Baker pick would have won Ford the election. But it is reasonable to disagree. However, as a timeline I'd say it is plausible at the very least.