Service manual specs shows 1" bore MC for drum brake applications whether 6cyl or V-8 & HD. Disc brake setup has 1 1/8" MC bore.

For drum brakes there is no mention if its used for power or manual. Here is a quote from the Service Manual. "The MC used on vehicles not equipped with power brake units is serviced in the same manner as the MC with power brakes, with one exception, the MC for power brakes does not include the push rod." Hope this helps.