Foxbody with no start issues

Looking for some help or advice. I've just recently rebuilt my 1991 LX with a 408 stroker motor and MSD ignition system, and Aeromotive Fuel System. Here is what has been done so far:

Verified fuel pressure running around 42PSI, and the motor has great compression, problem seems to be with the Ignition System.
So to start I did a wire tuck, and battery relocation to the trunk, to which I was extremely cautious to use the correct gauge wires, and all my grounds I sanded down the locations to make sure they made good contact. I have 12 volts, to the MSD box and when cranking it drops down to around 10 volts. Verified with all the on-line sites I can find that my TFI and PIP are sending a proper signal to the coil but it still wont fire with my MSD 6AL box connected. If I by-pass the 6AL box I can see a spark but it looks weak. I have talked with MSD numerous times, and done there box/coil test and which has me ground the white wire to body ground with key on and I get a GREAT spark. So to me there is definitely a signal missing when cranking to the coil.
I have replaced the MSD 6AL box, coil, and distributor all twice with no difference. Any help would be GREATLY appreciated.

Looking for some help or advice. I've just recently rebuilt my 1991 LX with a 408 stroker motor and MSD ignition system, and Aeromotive Fuel System. Here is what has been done so far:

Verified fuel pressure running around 42PSI, and the motor has great compression, problem seems to be with the Ignition System.
So to start I did a wire tuck, and battery relocation to the trunk, to which I was extremely cautious to use the correct gauge wires, and all my grounds I sanded down the locations to make sure they made good contact. I have 12 volts, to the MSD box and when cranking it drops down to around 10 volts. Verified with all the on-line sites I can find that my TFI and PIP are sending a proper signal to the coil but it still wont fire with my MSD 6AL box connected. If I by-pass the 6AL box I can see a spark but it looks weak. I have talked with MSD numerous times, and done there box/coil test and which has me ground the white wire to body ground with key on and I get a GREAT spark. So to me there is definitely a signal missing when cranking to the coil.
I have replaced the MSD 6AL box, coil, and distributor all twice with no difference. I have followed all the steps from link https://www.stangnet.com/mustang-fo...-checklist-for-fuel-injected-mustangs.787471/ and nothing seems to be pointing to the issue, except possibly an ECU issue.
Only last things I can think of is because I moved the battery to the trunk i only used 1 ground for my ECU ground in the wheel well and the original wire also also went to the battery. Or the other suggestion I heard was that it would be a good idea to separate the ECU ground in the wheel well from the MSD ground because the two together could cause an issue. For now I have sent my ECU out for evaluation, so we will see what they find, but any other help would be GREATLY APPRECIATED!!!