Your best bet is finding a used or restored set up. This is a big $$ upgrade for these cars. You will likely spend $2-3K to get all of the correct parts for the conversion:

$150 for floor brackets
$500-$800 for shifter handle
$1000-$1500 for all console parts
$100 for wiring


70 Road Runner 383-4 4 speed FJ5 & black guts
70 Charger R/T 440-4 4 speed FJ5 & white guts