Is the firing order right have not had any experience of V8 but two of the adjacent leads look to go to left side of pic would have expected them to alternate.
I used to have a P6 which was a V8 auto, standard 3.5, and it had exactly the same problem. The standard mechanical fuel pump was swapped for an electric one back in the fuel line towards the tank and that cured the problem.
From your first post do you have an electric pump already though?
Most fuel issues are spark related in the end. I’d look to replacing the ignition amplifier module and the coil for known good ones and see if that helps.