Ford: Fox body IRS?, bolts and nuts, stock ford

Question
Hello i have a 92' mustang hatchback, i have been looking at differant rear suspension options and i think i have decided to go with a IRS out of a newer cobra as the "cage" for the IRS will boly up to any 79-2000 mustang, i apels to me becase its a totaly differant setup than the stick live axle not just a improvment and its still "stock" ford so parts wont be an issue. How ever there are a few things im unsure of  like, are the springs the same,i dont mean in spring rate but in shape and size they look like they go in the stock locatin(but i assume il need a diff spring rate)will i need diff rent shacks due to the drop ove over 120lbs of unsprung weight? and finally will i need a short/longer drive shaft?
Thanks for any help

Answer
i have done 3 of this and what you want to do is install the complete unit with springs and all , also grab the mounting bolts and nuts.yes the drive shaft fits fine you can not use your quad shocks. in the front you want to use the springs out of a 4 cyl mustang to transfur weight better.and use moter mounts out of a conv.good luck