I did similar, but I have a breaker right off the battery.
I augmented the original wire. With the heavier wire.
I used this breaker
https://www.amazon.com/gp/aw/d/B08TWQMVH3?psc=1&ref=ppx_pop_mob_b_asin_title
If I actually saw one in person, I'd just buy it.
I can't make myself order one sight unseen. Not that I have done that before.
Partly because I'm not positive about getting anyplace to pick something up.
For a truck, Unless I find a bargain on a 2006 or 2007 duramax, I will stick with the 1994, if I ever get it on the road again.
I should have noted I was referring to a Suburban.
I've always wanted another Suburban.
Use only ACDELCO, GM or something else that's recommended on this forum.
A lot of people have wasted time and money on aftermarket thermostats.
Check everything before replacing your thermostat.
Has your cooling stack been cleaned lately?
Check your thermostat in a pot of water.
I prefer a toggle switch.
I passed on Leroy's harnesses a few times because there were things I want. A toggle switch for on/off. Prime feature. Mountable relay socket instead of a mountable relay.
Now I would just order his and change what I want. It would still save considerable time...