yes... I did this on my 1977 Grand Prix... when it was new. I put 100 watt halogens in the high beam location and had to add the relay breaker to handle the load off the high beam foot switch. The wiring had no issues.
Today you likely need to pull in new wires too. But using the fog switch on the multi function switch should be easy. Today I'd buy the KC harness for a start.
On the LED thing, I was a hater too. I was going to go with Warn halogens on the A Pillars but for simplicity, load, $$$ I went with 2 Kawell Side Shooter, $69.00. And I have a single LED bar for the roof. They all run thru the factory fog wiring. Took years to take the jump. Glad I did. They are a much stronger, smaller target for winter sand, salt.
https://www.amazon.ca/dp/B071DQRQ5Y/?tag=tjforum-20