Car won't start, electrical issue
 

I have posted this on some LT1 pages will no luck.
96 Camaro, Lt1 stroker ect. Battery has been relocated to the rear using a 3/o welding cable to a post up front, then the same for ground to engine and to starter. Using a cheap summit cutoff switch. If the car has a semi battery (1140CA) car will start fine. If I use a ford battery that fits in the box(1040CA) it will crank like a champ but not start. Checking voltage to the front lug it drops to 8.5ish volts with the ford battery. It has ignition spark but no injector fire with a noid light and has +voltage to the injecter. I have checked all grounds on the car and to PCM numerous times. Just replaced with a new Remi LT4 starter. bypassed the cutoff switch and have ran a jumper cable from the battery to the front post. However I can put the big battery in and it will start. I have noticed it looses around 3/4 - 1 volt from the rear to the front while cranking with the ford battery. Any suggestions is appreciated. Once it starts it runs fine. It has done this since I got it back togather with the battery relocate. Sometimes you can put a charger on the battery set to engine start and it will start but not always. Thanks in advance

Can you bypass the cutoff switch to eliminate that as a possibility? Sounds like somewhere along the line there is a questionable connection.

Tried that last night with no luck. Even with the long spand it should not drop a volt with 3/O cable,Am I thinking right?