vss is yellow wire coming out of speedo cluster(there are two-use the one from the speedo, not the tach)
You will have a problem with the vehicle speed reading initially-the Eclipse units are built to accept 4k-8k pulses per mile. The Alpha produces 128k pulses per mile. You'll either need a pulse divider or to add a signal generator(magnets) to the driveshaft--otherwise you'll show about 800 mph on the hwy
. If you're using the signal generator, don't forget about the net effect of geared hubs on the relationship between driveshaft speed and vehicle speed.