Torque converter & flexplate??

Alright so I’m currently unsure about the flexplate and torque converter I should use with my 76 duster. We are putting in a 1970 340, bone stock so I assume OEM crank (internally balanced). The transmission is a 904 and I’m unsure about the torque converter and flexplate to use with the 340 904 combination. I looked in classic industries and they only sold flexplate a for 318 904 and 360 904 combinations so I really don’t know if the 340 is any different than those. I purchased a B&M flexplate for the 904 with a 10 inch torque converter mount. I’ll link in my possible options and if anyone can let me know any suggestions if this will work or not. Also I’m pretty sure the answer is no but would a 9.6 inch torque converter work with 10 inch flexplate. I feel like it’s a dumb question but I had to ask.

flexplate:
B&M Flexplates 10231

Torque converter:
https://www.manciniracing.com/haytwister12.html