Mach1 Motorsport is a custom fabrication company in Australia that also performs engine swaps. Their own BMW E30 is powered by a turbocharged 4G63 inline-four that’s seen everything upgraded except the block. The engine currently runs a BorgWarner EFR 7670 turbocharger but will eventually replaced by a 7064 turbocharger. The 4G63 mates to a BMW ZF310 five-speed manual transmission thanks to a PMC Motorsport adapter and sends power through a custom driveshaft to a BMW medium case LSD. The company is also developing a swap kit so you can also swap a 4G63 into your E30.
Source: Mach1 Motorsport FB page (formally The Fast Farm) via PMC Motorsports FB page