i have contiplated this for a long time.
i have a stock 62 falcon and a
63 falcon thats on a 71 international chassis 4wd.
cheap and easy? (insert non stop laughter here)
however, the easiest way to go about this, is to
gut the entire car,
weld support bracing into the cab or body
weld doors shut
cut off all unibody substructure
purchase rear frame rails from summit, or other parts place that are ment for GM F bodys.
purchase 2 x 3 box tubing
and either a mustang II kit, or a straight axle.
either way, its a big project.