I'm tyring to figure out what part of the IRS cradle or control arms are "level" so I know where to put the brackets. So far, I'm thinking the pinion mount brackets are probably my best bet. They look to be perpendicular to the pinion flange.
Not to hijack this thread, but you should look up a build on here called "Twin Torino" by SVTforme, he put a Cobra IRS under a Torino and could probably point you in the right direction.