Welcome to the SMD forum!
So I just bought a truck the previous owner had stereo installed. The battery was relocated to the rear with a second battery. Truck has two alternators. Both alternators feed to a single power junction block. From that single block 1 wire feeds to the starter, one smaller one to the trucks main fuse block and two 1/0 run all the way to the back, one to each battery. The batteries are wired in parallel series. I don’t see any fuses anywhere. I’m hoping that this big of a job they were smart enough to fuse the lines and the fuses are under the box the batteries are on. All of the amps are properly fused. All in all the set up looks ok. It just seems to me that there should be some fuses closer to the alternators incase something happens? What do y’all think or recommend. Thanks.