One thing that might make this easier, is to use the B20 flywheel and pressure plate, and the B18 clutch disc. Or see if The B18 disc and pressure plate could be bolted up to a B20 flywheel. Or even see if a B18 flywheel will bolt up to a B20 crank. This is what Acme Adapters does to get a VW diesel engine to mate up with a Suzuki gearbox. They modify a Suzuki flywheel to fit the VW crank, then there's a simple adapter plate that matches up the Suzuki bell housing to the VW engine.