I hadn't noticed this comment before, but it still seems relevant...It is VERY unlikely there will be enough height and width to fit both the engine and electric motors in, so will most likely be loosing the engine and just keeping that as a spare for my 2014.
The best route I see is to loose the live axle at the back of the car, then build a more modern suspension at the rear with some custom driveshafts. Giving it direct drive like it would have in the volt through the original final drive.
The Volt doesn't have "direct drive" in any sense. Perhaps you just mean mounting the Voltec 4ET50 transaxle (without the engine) in the rear? The motors are connected to the outputs through gearing (including a planetary gear set that is used as a power splitter in hybrid mode) and a differential.