stock intakes are plentiful and cheap enough that if you have an e50 just get the 'square port' 14 mm and be done with it, even if you have a high torque cylinder that doesn't match, it don't matter.
za's are a bit trickier, the 14 mm tall intakes aren't really 14 mm and they are pretty rare, i usually make my own intake but you can get aftermarket ones '#1 grandpa' that treats sells with a spacer plate.
the restricted cylinders i've seen have a pressed in steel bushing, never seen one with a snap ring, you gotta grind that sucker out and it doesn't cut good because its steel. you are better off just finding a new stock cylinder if you get one of them.