Have you ever pressure tested a torque converter, I have chased a few leaks in that area and most of them end up being a leak around weld on converter hub.

64 Dodge Coronet 440. In progress
1998. Dodge Avenger. 8.35@165. 4400 DA
250” Neil and Parks Slip Joint. 7.36@183.
4600 DA
242" Mullis Dragster. 6.90@ 200mph