clutch size? best street clutch

I bought a used flywheel for my small block the clutch bolt holes measure just over 11.5" center to center. Is this a 10.5" clutch size? Also would like clutch kit recommendations stock 75 318 with 4 barrel and dual exhaust in a 66 Dart with 3.55 sure grip. Mostly cruising rare trip to the strip. Definitely need to be economical in price.