Reuse the intake manifold with all sensors and injectors off the a1 and put it on the b20b. You will have to change the block mount that hooks to your stock motor mount. Use the mount from the b18a1. Basically you need a lot of stuff off your a1 to get a b20b to work.

As for a b18b1, all you should need is the injectors off your b18a1.