By "direct drive" you appear to mean driving a differential though only one stage of reduction gearing, included in the final drive (the ring gear around the diff and pinion on the input shaft).- Can you "direct drive" a front wheel drive car (this would give me more donor car options)?
You can use a final drive unit (diff assembly or "rear end") from a rear-wheel-drive car, but placed in the front and driving the front wheels. It would be difficult to fit the entire motor ahead of or behind the final drive in most vehicles and using a typical rear final drive. Maybe an Audi or something designed to fit an inline-4 or even inline-5 ahead of the transaxle, with a short-nose final drive? The small rear-drive BMW seems like a more suitable choice, especially if you can jam that motor into the transmission tunnel.