The rim size was 14" and the tire size was E70-14 on the 340 dusters and on the regular dusters it was 735-14.
D78-14
They should have come standard with 75-series 14" tires
D70-14" or 735-14"
The original brochure can be found here: http://brochures.slosh.com/ It appears the standard size was E78-15B which converts to a P195/75R15 Some of the optional sizes were 7.00-15C, 6.50-16C,...
195/75-14 This answer is true with today's sizes, but at the time a Nova came with 7.75-14.