Are you sure our old Pintos are hub centric? The reason I ask is that before I went to 15s I bought a pair of 13" mini stock wheels and the hub hole in the wheel was off center to the point I couldn't get the lug nuts to seat properly. Using a die grinder, I opened up the holes to make them fit, had a tire shop balance the wheels using a lug centric adapter and those wheels worked perfectly.
As for the adapter, numerous companies make 4 to 5 lug adapters but I didn't use those. I used the 4.25" 1 inch spacer and bolted the spacer AND the wheel to the ARP wheel studs. My team ran the car very hard for 12 hours on a road course and never experienced any vibration, odd tire wear, or any other issues plus we didn't have to grind anything for clearance.