[Accelo]

Did you convert the wire from the alternator to a #8 wire. If you are still using the stock style feed from the alternator it is grossly undersized.
In the picture it looks like the battery charging wire is too small, it it is connected to the battery not the starter.
The #8 alternator wire has to go to the starter or directly to the battery.
My friend just went through this with an LS3 conversion and a larger wire solved his issues.
You can get a kit to convert it which will include a Mega fuse to protect everything downstream from the battery. I included a picture of the fuse. It doesn't show the covers that come with the fuses.