If he kills his soul reserve, yeah totally, all he needs to do is land a blow that would normally kill and one of his souls takes the damage instead, dying in Alucard's place, if Dio can land lethal blows enough times to deplete his soul stock, the final hit would kill perma. The issue is how many souls that is, it's half a million if I recall, basically Dio would have to punch Alucard half a million times. So really, it depends which way we're equaling, if we equal it to Alucard, that many blows seems unrealitic, if we equal to Dio then it should be doable, especially with time stop. Depends on that really.
Incap is also an option because I dont think Alucard can get around being frozen, it wont kill him, and it wont overcome his regen, but if Dio kinda just, leaves him there, that would work from what we know.