New to forum, putting a tach on '94

Whats up ya'll. Just got my 1994 Standard cab 5-speed with a/c for $2900. I want a tach, what do I connect the green wire to? I already replaced the shocks and changed swaybar bushings with polyurethane... tightened it up real good! Searching the junkyards for a 4x4 front next week.