You're asking to do a completely custom rear suspension and drivetrain that no ones ever done before, then asking how hard it will be...
No one is gonna know, the closest anyone has ever done with that is I believe ONE guy who swapped in the rear suspension out of a C4 Vette. Unfortunately, that whole build thread doesn't exist anymore. It was Turbobuicks.com, but the links to it doesn't work anymore.
Good luck though!