Yes. You'd have to remove the stock heatsink and fans from the card you were putting in, which would surely invalidate its warranty straight away. Then you'd ha

Yes. You'd have to remove the stock heatsink and fans from the card you were putting in, which would surely invalidate its warranty straight away. Then you'd have to somehow mate it with the heatsink bases on that side of the Mac Pro's thermal core, not something that's not likely to be straightforward if the replacement card's make and model don't closely match that of the stock card it's replacing. And that's just the beginning of the possible problems.