Measuring the Headrest
Well, based on your illustration it looks like you are measuring to the back welt cord - unless it's just the drawing. I measured to the front cord and got pretty close to 9". Of course there is a chance that 40 years of differing climates, etc. or variances in manufacturing might have caused that difference. At least we're sure it's not the 7 inch version!
Oh - it will be at least spring before I cover the seat - Too cold and wet right now. This should be reasonably easy. Get yourself a QUALITY pair of hog ring pliers and take your time. I did the entire interior of a 72 Cutlass a few years ago and I'd never done anything like it before - came out great!