Start with the resistor version (consideration for other drivers nearby, in case you have no radio) of the stock heat range in Bosch, Beru, Autolite or NGK plain copper type. Many have the opinion to avoid Champion brand. After some running, pull the plugs and examine the colour of the tips;
-> Light to medium tan or beige is perfect.
-> Very clean, recheck a few hundred miles later.
-> If too clean, or there is any signs of blistering, then move one heat range colder.
-> If dark brown or any shade of black... a heat range hotter.

Euro & Japanese brands: higher number is colder
US brands: higher number is hotter

The final answer will depend not so much on your "specs", but on carburetion, timing advance curve, the fuel and also your driving style.