I'm using a universal Ebay special expansion tank. This does not go in line on the large 1.25" line like the factory one. I have an 1/8" npt fitting tapped in my 1.25" coolant line high spot coming out of the engine, the other outlet feeding it comes off the turbo water outlet. The outlet from the tank (bottom hose) goes back to the motor and is tied into the suction/low pressure side. The top line is pressure relief to a plastic tank.
I prefer this style as they do not interfere with flow. These do take a little longer to get the air out but once it's out, it's out.