Electrical problem after drive-train swap

I just finished a drive-train swap and on the test drive, the engine continually stalled whenever it was put in gear unless allowed to roll or unless gas applied. The acceleration was also sluggish and not smooth. Eventually, as I was driving, I lost all power to everything and had to push the truck off the road. The battery was very hot but no fuses had blown. I removed the battery fuse to prevent fire just in case.

I know I broke a ground near or on the firewall that I forgot to replace. Could that cause the poor engine performance or possibly even the apparent short? The truck ran fine before, just had no reverse. I do not know where the ground strap was, exactly. It just fell out as I was dropping the old transmission. Should I just run a new strap from block to frame or block to body, or both?