Most of fuse boxes have main wire rated for over 100 amp, but if you draw 40 amp for tool and use other accessories, that might be a concern.
It is just easier to add additional cable to battery clamp and put circuit breaker on the line.
This is how I wired 1600W inverter on my camper, where 100amp breaker has a switch, so easy to keep it off and turn on only when needed.
Bear in mind that hot wires run under the bed are higher-risk issue, so plan to put them in additional sheeting.
I had several issues on frame-bolted ground wires.
Corrosion gets to them and lack of power is hard to troubleshoot.
Manufacturers do it, but they hope the truck will come out of warranty before the corrosion-related issues will become reality.
I have no problem with forum script.