[Rwillia4]

Call these guys. East County Drive Shaft (619) 447-3336. They are in San Diego. I had them shorten my driveshaft and make it stronger. They installed beefed up u-joints. I want to say the back one was from a toyota (metric) same size as the bimmer but stronger. Front was replaced with something stronger.
Cost was ~$200, took a day.

His shop is down the street from an old cobra builder/mechanic so he has done many in the past.