I can relate.
In late 04' early 05', I was 415 (6'4"). I was lifting 2-3 times a week, no cardio. I'd get winded going from the couch to the fridge (lots of that).
Not trying to be a dick here, but you may be better served getting some ECA and concentrating on your cardio. You'll be supprised, in no time you'll be down to 350 and you'll feel way better. Less stress on the pump. At 255, I'm actually stronger than ever, with a little help of corse.
But for health reasons, it might be a better idea to shrink a little first.