4 speed swap question

I just pulled the 904 tranny out of the 73 Dart Sport today. we are going with a 833 4 speed. I have a 360 in it. I put a new B & M flex plate on this when I put the 904 in it about 6 months ago. what kind of a flex plate will I need to put the 4 speed in this car. I have not done this in 40 years so I need to learn it all over again. can you tell me what I am going to need here.If I cannot use this flex plate, I am going to sell it. thanks,Bill