It's really still quite confusing, but I'm beginning to piece it all together. From the registration form, one can register for the Friday WGI 3 hr economy drive(I think it's an economy drive), or the Saturday TSD rally or both. Since the Friday WGI drive is an economy contest, I think, then there would not be a target speed, just an acceptable range of speeds, and potentially some corner speed limits.
I'm not sure whether a navigator is required for the Friday WGI run, since one is only driving for economy on a well defined circuit for multiple laps.
I guess I'm going to have to make the call. Rules for the TSD rally are probably the normal SCCA Rally rules, but the WGI economy run is an entirely different animal.
It would help if they would update the page and cite some rules for both contests. Guess I'm going to have to make the call