Advice needed

I just recently bought a 66 dart. Its got the straight 6 in it. I'm not a mechanic but have some knowledge and with the right guidance I can fix most things. The car is in great shape but the temp gauge, odometer, and speedometer doesnt work. The car has a wicked paint job and nice interior bit i was hoping for suggestions on ways to add horsepower and other cool thing I might be able to add. Also want to add other gauges to it. Is this possible? Thanks everyone!!