There's a chap on E30 Zone selling an M52B28 crank and 130mm con rod. That plus a M20B25 and you'll have a nice 2.8ltr
Build it take the current engine out and your sorted for a winter project
A quick call to Ant @ A-Tech and the ECU can be easily sorted for the higher capacity with a new chip.
Not sure on the power but should end up around or above 200bhp with a wedge more torque as well.