A lot of people with fundamentalist upbringings still have trouble getting over the fear of hell, something that I'm not sure natural-born (rather than born-again) atheists can truly understand. With that as a preface, I'd hope I'd have the balls to say "no" and die as I've lived.
Would you rather?...

if there were some omnipotent supreme being and they were vindictive enough to believe if you followed no book or the wrong book or the wrong bits of a book you were not good enough for their life everafter, regardless of how you have lived your life,i think they would more likely than not be a bit of a twat about the whole deathbed conversion thing. and rightly so too.

I'd probably laugh at him. There are numerous different belief systems, all claiming to be the only true religion and say that the non-believers will get some kind of horrid punishment in the afterlife. There's no reason why the christian belief should be preferred above others.
Besides, even if the pastor's belief system would be correct, do you think that God will accept this kind of reasoning to let you in to heaven? "I gain more from believing so I believe in you"?
I'd love a chance to do what Voltaire did. For those who don't know when he was on his deathbed somebody got a priest to come to administer the last rites. Voltaire flatly refused. The priest then asked Voltaire to at the very least denounce Satan and Voltaire replied (translated), "No, now's not the time to go making enemies."
Let's say you were on your death bed and a pastor comes and and shares with you the gospel.
Would u rather accept the gospel not risking any chances of u being wrong?
or
Would you rather reject taking the chance that he may be right