Actually, I’m not sure that that would tell us if Romney is “really” a pro-lifer. Politicians have to pick their battles, after all, and given the political climate in Massachusetts, he might well have chosen to keep his pro-life sentiments to himself, given that they’d not only be politically damaging but would make no difference in terms of policy.
Another possibility is that the change of heart preceeded the choice not to seek another term, since running in Massachusetts would have required him to maintain a publicly pro-choice stance, and he couldn’t stomach the disingenuous that that would require. If that’s the case, than the question is totally inapposite: He only would have chosen to run for a second term if there had been no conversion.
In any case, we should be less concerned with what a politician believes in his heart than in what he’d do in the real world. On that score, my sense is that a President Romney would indeed be allied with pro-lifers most of the time.