Hi Tom.
Sounds like a perfect candidate for ABS, but I don't know if such a conversion would be practical.
I am not familiar enough with the vans to be able to anwer any of your specific questions - all I have learned about the Chrysler brakes are specific to my Concorde (and the mechanically identical other LH vehicles) only because I own one.
You may not like this suggestion, but you could put some dummy weight back there to help the situation.
I hope someone else can provide the information you need for a conversion. Salvage yards would save you a bunch of money if you do a conversion, and maybe buy new aftermarket rotors and pads.
Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")