Tomohawk - check out this thread http://www.hybridz.org/phpBB2/viewtopic.php?t=28380&start=0
BTW, I used old Stewart Warner gauges in my dash. http://www.hybridz.org/Review/0002/GTO_31.jpg
The "Simpson" dash looks more like the original GTO dash but does not have provisions for heater controls, radio, vents, etc.
The "Alpha" dash actually goes over the original sheet metal skeleton and has provisions for all the original controls, vents, etc. Also, the Alpha dash was set up to use the original Datsun Z gauges if you want to.