Cracked flexplate question

Thanks furyus2, I hadn't thought about the converter being bad. I will check and see if my brother-in-law has a spare at his shop. They used to race Mopars so there is no telling what he has laying around that I can use for troubleshooting.

If he has an externally weighted converter for a 904, I will still need to figure out which B&M flex plate to get.
If he has an internally balanced converter for a 904, I can get the B&M 10239 flex plate as mentioned above.
I guess another option is to take the weights off of an externally balanced converter and still get the 10239 flex plate.

Is all this correct or am I wrong in my thinking? (wouldn't be the first time)