LS swap alternator wiring

[Hidesertchevy]

72 c10 LS swap 5.3 gen 3. On the original truck side of the forward harness, do I need to hook up the thick red wire going to the alternator? Also do I need to use the junction block on the fender next to the battery? Thanks

[LS short box]

Not sure how a 72 C10 was originally wired but keep in mind typical LS alternators are 120 amps? so the wires running to and from from need to be a large enough to handle the increased amp load.

[Hidesertchevy]

I know the oem LS wiring to the battery will charge the battery. Just not sure if I need to also hook up the truck side forward harness to the alternator also?

[A1971Blazer]

you might want to use a larger wire with a fusible link from the alternator and connect it at the starter on the same lug that the main battery cable connects to.

The original wire is fairly small gauge. The later model alternator will be a higher amperage and may overload the existing wire.

You will need to keep the wire from the battery to the terminal on the fender as this wire feeds thru to the fuse block and powers everything inside the cab along with the lights, switch, turn signals, accessories, etc...

The factory 5.3 has a fusible link from the alternator to a little red junction box that connects it to the positive battery cable.

Keep in mind, there are other ways to do it....this is just one way.
Essentially what you're looking to do is connect the alternator output to the + side battery in some way (safely).

Here you can see the fusible link as connected to the battery cable on a 5.3 taken from a 2001 Tahoe