Thanks for all the great replies. I was finally able to get the car off the jack stands and take it for a ride. Once I removed the return spring from the pedal support bracket under the dash and adjusted the clutch fork rod accordingly, the diaphragm style clutch felt great (with the spring in place the clutch pedal has a slight hesitation on the return swing and also feels a bit odd on the way down). After the first few shifts the clutch completely left my mind and I wasn’t even paying attention to it, which is a good indication that it felt correct. It’s just as smooth as the lever style clutch with the added advantage of less holding pressure when the clutch pedal is to the floor (i.e. waiting for that red light to turn green).
Just noting again that this is a stock 289 with a holley intake and 4bbl carb with a 4spd top loader and a standard diaphragm style clutch.
They are pretty sweet for that reason alone. Almost makes me want to do a 5 speed conversion. But then I get in traffic around here and think better of it. Even though the gear splits aren’t as good, I’ll stick to my c4.