As for brake pads, the old Carbon Metallic pads that AutoZone used to have worked fine on another car I have. They are still around, with a website. Their claim was shorter stops with just a front brake pad change (to their pads).
On the edge of the brake pads, there are some numbers/letters. This code identifies the pad material as to coefficient of friction between the pad and rotor. There are two letters, the first for "cold stops", the second is for "hot stops". Letters go from "C" to "F", with "F" being highest. Aim for "FF" markings. Factory pads are bonded rather than riveted. The other code items define the maker of the friction, the "batch", and the coefficients I mentioned.
The purpose of the slots and holes is to allow the gasses produced by the brake pad, as it works, to better escape rather than stay there. It's supposed to be "the gas layer" that causes brake fade, so getting rid of the gasses is supposed to help. BUT unless you're trying to hold down the speed of the car (and trailer) down a long descent, OR are into heavy road racing, these things can be more "show" than go, in reality.
Everybody's headed toward ceramic pads. Ceramic pads used to be what the LeMans people used, due to its higher heat tolerance. On the road, the push is because of legislation to get all of the copper out of brake friction materials, so that means "ceramic". Ceramics are more abrasive to the rotor surface than other types of friction.
Personally, I still like the feel of good metallic pads biting more as they get hotter. Now that they are "out of favor", the prices have decreased.
Looking through the Raybestos (and similar) online catalogs, there are listings for "police" and other HD uses. Make sure that you have 11x3 brakes on the back, too! The wider shoes should fit the backing plates, but you might need new drums for the wider shoes. If they are not already there.
On the other hand, the sizing of the brakes appears to be very ample, with factory parts. Find some better brake pads AND don't forget about the role of tires in the stopping performance mix! Chrysler products always had better braking response than similar GM cars, with less pedal travel. Remember that in full trailer mode, with the HD trailer package, the New Yorker was rated to tow a trailer of about 12K pounds. So, aim for the HD option specs!
CBODY67