Good question.. I recently rebuild the engine ( stock 68 383) also installed new mcleod clutch kit and I also had my original flywheel resurfaced. When I put it all together I experienced severe clutch chatter only in first gear. I drove the cuda for 2 seasons the chatter stayed the same. I tore the engine out and sent the clutch kit back to mcleod for inspection, they told me my pressure plate was out of alignment so they replaced it and told me my disc was not wearing correct due to the mis alignment of my pressure plate or incorrect resurfaced flywheel. So they did work to my disc to get it back to specs.
The machine shop that resurfaced my flywheel closed down after many years of business. That's why my plan was not to risk it and purchase a new flywheel or now maybe ship my original flywheel out of town to get it professionally re resurfaced...