Clutch Identification

I have a 79 l82 with a 4 speed manual box and the clutch is starting to slip when I give it loads of power, is there any way of identifying what the clutch would be as I believe there are various diameters and different number of splines on Chevy manual clutches.
I would like to get the clutch before tearing it down to replace it as parts deliver over here is a bit slow.