Again I said this was a budget (& quick) way of doing things, you can use certain etch primers as a substitute but even I had various etch primers flake off after awhile, and what I did with that aluminum primer has held up for 3 years so far. These are available at all hardware stores
After you sand the aluminum and then clean with either alcohol or lacquer thinner make sure you start using the primer as soon as you can so the oxide barrier doesn't form again. This is the reason why paints flake off so quickly is because of that.
That was the main problem with some of the aircraft that I worked on in the past, especially in humid climates, some derp Airman (or even Specialists) thought it was ok to simply spot paint a panel with out bringing the part into a controlled climate area. Not only did that humidity affected the paint, that oxide barrier formed quickly because of that as well.
Rustoleum and Duplicolor etch primers suck, do not use.
The other primers that I've used that work would be these but pricey & not widely available: (And they hold up to heat fairly well)
ACID#8 Acid Etch Primer - U-Pol
Spraymax 3680033 SprayMax 2K Epoxy Primer | Summit Racing
As for heat, I wouldn't worry about it too much, that 4.0L in that Jeep likely runs hotter than your car, I know for a fact it runs hotter than my 360.
And also why specific paint prep work used on aircraft is not the same as what you do on cars.
I've used that Spraymax epoxy primer then top coated with paint and then used the Spraymax 2K clear on an aluminum Speedo housing on my old Motorcycle in 2010, still looks good to this day. And that's with 13 years in the sun and several tens of thousands of miles.
*Disclaimer* Be careful! Spraymax products especially their 2K stuff has Isocyanates in it, please use proper rated respirators when spraying these.