First off, what size are the bostons? Front/rear sizes. 5-1/4" or 6-1/2" will fit up front while only 5-1/4" will fit in the rear. More than likely your old brackets won't work with the door panels and new ones will have to be bought/made. IA performance makes a great set of spacers. You can email them with the mounting depth for the bostons and they'll tell you if it will work.
Also, the frpnt speakers dont have a crossover...the tweeter just has a filter capacitor.