You forgot to mention the tacho as the "10K monster tach" to say to police "I'm a hoon, book me!", pointless really, why waste good money buying one when your car already has one..
but seriously, if you don't want to go overboard, I think you'd only really want the temperature guages, don't want to go cooking your engine now :lol:
Mabey an Air/Fuel guage too just to make sure its not leaning out..