I like the 727, but for your application with a light vehicle and only running to 600 ft, the PG would make sense. The 1.76/1.80 first gear and all the gear you want in the back (5.13?) since you don't have to worry about running the 1/4 mile. But then it will overrev if you race at another track (1/4 mile).

A simple 727 freshen up with a good valve body is all you need, IMO. And that would be a good low dollar approach.