looks like a Horstman HDC-5, may be a 2 disk clutch?
You can find all parts for it here.
But if you’re gonna run autocross, you may wanna consider something more durable, like a 3 to 4 disk wet clutch. I dont know how much you weigh, but if you’re over 225 lbs, I highly recommend to stay away from your current clutch, you will burn it at no time.
The clutch is a single disk, really can’t tell from picture. There is a large nut that holds the clutch together.looking at exploded views hdc-5 uses cap screws. maybe an hdc-4?
Defiantly not a HDC5 because as everyone said a 5 doesn’t use the big nut. I say HDC 3 OR 4 but according to the picture it is junk so I would through it away and get a newer Horstman HDC5 2 or 3 disk depending on your weight. The reason I say it is junk is the front plate appears to be broken right at a weight attachment point and it would be hard to find parts as they haven’t made that style clutch in some time.