Clutch disc size?

[Lobo'74]

My '67 C10 has a hot rebuilt '79 350. 325-350 HP. No idea what the torque is. It came with the truck when I bought it. It has a "stock" '79 350 C-10 clutch and saginaw 3 speed. It sounds and acts like it ate the clutch and transmission. Haven't pulled the old stuff off yet, but clutch was pretty far gone anyway . . . I want to use the Sachs/Borg & Beck high performance clutch set for a replacement, either the 350 ft-lbs set or the 450 ft-lbs set.

Anyone used either set? Local mechanics/hot rodders say it works well as a high performance clutch, but has less pedal effort.

What size is a "stock" '79 350 clutch? 10.5", 11", or 12"? I have seen a set listed as 10.75" also, but I don't believe that would be a stock GM size.

Thanks for any info.