Engine swap 318 to 360
B&M 10239 flex plate will mate your 360 to your 904. If you're going to put the 360 in as a stock motor, you don't need to worry about buying a new converter right now. You should probably install a new front seal in the transmission while the motor is out though. Just pull the converter out, replace the seal and put the converter back in. No biggy and a seal is cheap.