If you are going to drop a OBR FM 30.5 long rod in, you will need the TR alluminium gear box, super heavy duty driveshafts, uprated cups (phatdad), blackbone 2-speed 18/56 & 22/52 minimum for the drivetrain. Them Badboy engines will find all the weakness's in your baja real quick. I'd seriously think on getting one as the torque rips it apart.
Definitely get the 30.5 over the 27.2 as it's a much better engine