Your honest opinion

That one guy said
Based on what I've seen, as long as I am not drag racing it (check), not running more than 500ish hp through it (check), not running extra wide tires (check), and am only pushing a relatively light A-body (check) the 8.25 should be more than adequate and the appeal is the availability of them in junkyards today for parts such as lockers and disk brakes

I might agree - if you already had an 8-1/4 in your car. But your original post suggests that you don't have one yet and were thinking about picking one up. You asked for honest opinions, and mine is if you are going to go through the time and expense of an upgrade, it is best to do it right. If I were you, I would cut down the 8-3/4 you already have.