ordered a 10239 b&m flexplate. going to swap my 904 with stock converter, use the stock driveshaft from my other slant 69 dart, swap out the 1350 yoke and see what happens.
Process of elimination at work here, I just hope it doesn't get too expensive for you. I remember pulling the trans out of my car a couple of nights trying different things.. I got to where I could have it out pretty quick. I had access to a lift though. Good luck.