Just so you know, the XR7 wiring harness is completely different than a standard. The XR7 dash will not work in a standard unless you change out the entire front wiring harness including the alternator and voltage regulator harness. There is also the issue of the harness for the courtesy light switches in the center of the dash. You can add a tach to the standard dash very easily.
The stock tach is designed to be in the coil drive circuit. It won't handle a lot of current so you might want to verify that it is possible to use it with the coil on your vehicle. There are a few tach adapters that might work, but the best solution is to use Rocketman's three wire tach. It looks stock but hooks up conventionally. You won't be able to use the factory ammeter with a one wire alternator. Rocketman has a very nice voltage meter that keeps the factory look, but will work with your one wire alternator. The one wire alternator doesn't use an external voltage regulator, so that won't be a concern. You will need to change out the pressure sending unit for the oil pressure gauge, but that should be easy. Probably the best thing is to buy a hacked up XR7 harness since you would be modifying it so much any way.