There are many options and as seen, many recommendations. You can also get a variety of clutch disc materials. Reading about those experiencing "chatter" could be due to the clutch material selected or supplied with the pressure plate - so this is important. I used a carbon fiber disc and it would chatter - but was told it will. However, the wear/abuse factor was better.
The clutch discs have differing designs. Some are the typical/conventional fully round disc while others use the paddle style. I have not used the paddle style, only the conventional discs feeling more surface area grip better and the paddle type my require a stronger pressure plate (pedal force) to clamp it.
Clutch discs can be had with a "solid hub" or "sprung hub." For a street application you want a sprung hub.
Clutch discs can be had with a "marcel spring" or not. You want the marcel spring.
Both of these above absorb the shock of the clutch when let out, especially when dumped.
You want a diaphragm style pressure plate that will provide a lighter pedal effort. The 3-finger Long and Borg & Beck pressure plates provied big clamping forces, but take 2 left legs to push in. They won't slip with big HP and wide tires, but you will not be happy if you get stuck in traffic or that long line going into a car show.
The diaphragm pressure plates have either a raised or flat finger set-up. Either will work just fine. The problem here is the throw-out bearing length. If the kit is not specific to a Pontiac, you may receive the wrong throw-out bearing. There is typically a long and short, there is also a mid length not to often used. I used a McLeod set-up in my '68 Lemans, and was sent the wrong length throw-out bearing - I believe it was for a Chevy set-up as the clutch fork is different. Of course I put the transmission in and the pedal went near the floor, so the clutch would not release. Not a new experience as I learned this in my youth, but assumed McLeod had included the correct throw-out bearing. Had to pull the trans and purchase the correct length throw out bearing. Enclosed a photo for illustration.
The type of pressure plate style also dictates what the mating surface of the throw-out bearing will be. Some have a flat mating surface while others will have a more rounded surface and I believe are called "self aligning." So should you have to get a throw-out bearing because your kit sent the wrong one, make sure your replacement has the matching face for the diaphragm selected.
The Pontiac uses a 10.5" set-up, but if you get an aftermarket steel flywheel (better choice over the 50 year old cast flywheel) it will have a dual bolt pattern, 10.5" and 11". Again, more clutch disc surface area, the better the grip. So the 11" set-up is the better option. I have the aftermarket flywheel and am using a 12" set-up by McLeod. It bolts up to the 11" bolt pattern, but provides more surface/gripping area. I have not installed/used it as of yet, but it was a recommendation from a friend who had a blown big block chevy on alcohol in his street car. He said it had an easy pedal effort and never had any slipping out of it. So I went with the same set-up.
So do some research versus taking opinions and then decide what you may want using the opinions to supplement your potential choice for a clutch set-up.
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