I just switched my '67 to a tach dash. You lose the oil pressure gauge and the useless amp gauge. They are both replaced by idiot lights in the tach. The hardest part of the switch-out was figuring out the correct wiring and how to get the idiot light for the alternator to work. The oil pressure light is simple. Let me know if I can help. I have a few web sites I can send you with diagrams.
Anthony
Anthony