1200's the stuff you want and ideally some cutting compound (T cut will do) for the final layer just to get it really nice and smooth. To be honest though, if it's in the engine bay, I probably wouldn't worry about cutting compound but any rougher than 1200 and you might scuff the lacquer.
Most Lacquer is alright with moderate temperatures once it's fully dried but it does tend to yellow quicker. I would be tempted to go for flat back high temp paint (hammerite will do) on anything that'll see high temps though.
Hope that helps!