Header leak

I've got a 74 duster 318 /727 that I put a set of dougs 453 headers on and summit exhaust system. Had no issues until recently it developed a leak on the passenger side that I cannot seem to get rid of now. I've tried new Doug's gaskets, aluminum gaskets and recently remflex and its still there. Has anyone had this issue the leak is on the middle ports passenger side. Possible warped flange? I also noticed the number 8 tube sits really close to a bump out in the wheel well where the a upper control arm bolts in could it be tight enough that maybe the header is pressing against that bump out when the motor is running and breaking the seal?
Any suggestions or experience would be greatly appreciated.
Thanks.