synthtk did a great job with an R33 Skyline instrument cluster. The stock GTST tachs go up to 9,000. I do believe the GTR's go 10,000 RPMs.
http://forums.hybridz.org/showthread.php?t=119780&highlight=tach&page=2
Autometer is the easy way to go.
Evan,
Did not intend to make you look like an ass. I never knew a 10k tach existed either till I got the Fairlady Z owners manual. It took 7 years for the question to be answered anyway.