Doors make terrible enclosures. The older the car the more horrible the enclosure.
Unless you have power windows and locks, running wires to the speakers alone is a practice in futility ... nevermind that speakers in the doors ... in doors that were never intended to house them ... have relatively short life spans.
Then of course there's the direction of the sound. Speakers in doors usually fire into the seat, legs, under the legs and into the trans housing. If the door were the optimal enclosure, the placement is anything but.
The kick panel is your best bet. With E-bodies the mounting depth is the issue, but wiring is a breeze. Any route you go you'll have to hack into a panel. Unless you get the kick panels from Classice Industries. Those only house a 4 inch driver though. Better sound placement, but not much behind it to balance out the 6x9s driving the rear deck.
For the kick panel you're going to want something with a mounting depth of 2 inches or less for a bottom mount. Top mounting you're constricted by the parking brake pedal. You can off set it for clearance. If you don't ... well you've got about an inch of top mounting depth to work with.
Polk's DB651S fits the 2 inch requirement when top mounted, and is low profile to boot ... you'll have a half inch to spare.
Kicker's 40CS654 cuts it close with bottom mounting, plenty of room with top mounting. You would probably have to space the parking brake pedal with this one unless you did a custom grill ... which isn't hard to do.
Rockford Fosgate P165 can be bottom mounted no problem. Top mounting runs into the same issue as the Kicker.
The Infinity Reference 6032si is either or with room to spare. The tweeter doesn't protrude above the mounting ring.
The JVC CS-V618 is a good cheap speaker that just may squeak into a bottom mount, but a top mount would be no issue. 25 bucks at most places, on-line or walk in.
Personally, I'd go component.
Precision Power's PH2.65 is a top mount only I believe, but it's super slim and low profile. You can slap it almost anywhere without a clearance issue.
Or you can drop a half grand on a pair of Focal Polyglass.
If you're insistant on door mounting, get marine grade speakers and be sure to use dynamat or second skin for sound deadening.
