Whether you want to run something only slightly more realistic than the Whacky Races using the QAGS ruleset or intend to retool this excellent concept for a real-world interpretation of international spies, there is a wealth of ideas and materials here.
After a brief introduction which sets the scene with a bit of flavour fiction and makes the assumption that you want to play a game set in the 1960s, it dives straight in. Chapter 1 develops a background based on the fictional Global Racing Group which organises international races and has some very interesting ulterior motives (which characters may never become aware of, depending on how you decide to run your game).
Next, Chapter 2 takes a look at 'real world' racing of the 1960s, with a brief mention of some things that didn't happen then for those of you who weren't around at the time. Then Chapter 3 looks at the sort of characters that might play a role in this game, concentrating mainly on actual drivers and replete with sample characters, and Chapter 4 covers vehicles and the rules necessary for running your races - useful if you intend this as a standalone QAGS game or are using the spy 'core' book Sex, Lies and Ultraspies. (If you are using a different ruleset, you may prefer the chase rules presented there instead: Spycraft 2.0 has particularly good chase rules, for example, and the rest of that game is quite compatible with the tongue-in-cheek approach of this book.)
The final section of the book is a full-blown adventure, Who Killed Team Unity? This is primarily centred around a race but whilst that's the main focus (until the climax, that is...) there are a few side bits that take it beyond that and will provide scope for future adventures both on and off the race track. An appendix-full of suitable pregenerated characters are provided if you want to jump straight in, or you may prefer to come up with your own.
Overall, Spy Racers is a brilliant core concept for a spy/adventure campaign, and it's open to you to play it as presented or go for a more realistic (or at least, thriller-style) interpretation. I can see it working with Spycraft or Night's Black Agents, or even if preferred with a superhero game. Lots to think about, to inspire you even if you don't play QAGS (why not, it's a fun game... even if you also like more realism in your alternate reality most of the time).