75 duster disc swap

ok guys sorry to beat a dead horse...i have searched and read tons of different articles but am still a bit confused on the particulars that apply to my application....its a 75 duster was slant six very soon to be 318... all the info i find is converting pre 72 to the 73 up disc stuff...does this application apply to me? what about the kits that say up to a '72? PLEASE HELP!!!! THANKS!!!