So, I've basically just have to find something specific for the dart, not necessarily the transmission. I've looked and couldn't find anything through the big name parts places. Found a few on Ebay.
x2 it's the same on all A bodies from 73-76 any engine or trans. I sell them for $50-75 blasted and painted but I'm currently sold out. Many other members here do also. You might check with Justin (ply30) on the board. He's parting out a bundh of 73-76 A bodies.
Good Luck!