10" clutch kit comes with 9 1/4" disc.

I ran into the same problem, last year. Sent the clutch back. Don't remember what brand it was, but I did contact the company, and was told that was correct. Purchased a "Perfection" brand MU-1525-1, and it had the 10 inch PP and disc. However the throw out bearing used a plastic collar/housing. I had heard of these breaking at low mileage. Called Perfection, and they sent me a TO bearing with a metal housing. Have not installed the clutch yet.
This is for my 84 D-100 slant six A-833od, that I use to tow my race car.