Sorry, I don't have any authoritative numbers on the max revs the 2.8 and 2.7 kits can sustain. However, what I do know is that HKS shift their drag cars (R33 and 180SX) around 9,500 rpm (using their 2.8 kit), and make peak power just over 9,000rpm with the huge turbos they run. This shift point also tends to apply with other tuners that use the 2.8 kit in their drag cars.
With 2.7 kits (eg. Trust, JUN, etc.) there is evidence of RH9 cars taking the engine to 10,000rpm. However, this appears to be the upper end. Tuners with shift points at 10,000rpm or later tend to keep their displacement below 2.7 litres (eg. stock stroke with a 1mm overbore piston).
Apologies if I'm not exact with the numbers as I'm going from memory based on articles in the Japanese mags.
Cya O!