You'd strip the sides off of the nut before you'd break a stud(no pun intended). The block is aluminum and the studs are steel. They're not going to sieze together as badly as steel on steel. If you don't want to take them off then you shouldn't do the manifolds. Yes, people have done it without taking off the manifolds and haven't had any problems, but there have been people that have had to replace their engines because of this. This isn't the way you want to do a 3L swap.
