You could try the stock tweeter out with the new mid but you probably less than satisfied as most component sets are designed to work together.
I would suggest mounting the tweeter in the kick panel it's easier access and you'll get better imaging because the distance from the tweeter to your ears will be close to equal.
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Ill say i go by His and Al's thoery of "Your getting sprayed" Doesnt matter what it is. Grandma in the 1982 LTD is gettin the bottle.