Tony, are you running in the Targa or Touring class? That makes a big difference, you don't need the sophistication if you're in Targa, but for touring you need a full-on TSD computer like an Alfa or Timewise if you want to be accurate.

OK, so, in that case the basic things you need are an accurate odo that has an adjustable factor, and a stopwatch.  Any odo would do for that, with a separate stopwatch. Terratrip, Brantz, Alfa Pro, etc.

You could go more sophisticated with something like an Alfa Elite, which will give you either a countdown display to the end of the stage (so you just have to get there before the time runs out if you set it to the target times) or an early or late display (if you calculate the speed needed to cover the distance in the given time, then just keep it early all the time and you'll beat the target time), but this may be more than you need. An Alfa Elite is great for Touring, as you can use it to stay on time all the time and at the finish.

Yes, you are correct. I guess I'm biased, I wouldn't be big on navigating that kind of event with only a stopwatch and a calculator.