You could have anything from a 10" to a 12" clutch depending on what flywheel/bell housing combination you have with that engine. It's best to remove it and determine what it is. Also match up the release bearing. It will save you untold misery.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine