Interesting response from McLeod. It appears that I had a 100 series disc in the original kit I purchased, though the box said it was a 500 series. The new clutch is a 500 series so I'm excited to see what the differences are.
The old disc is what we call a 100 series disc. Link - https://www.mcleodracing.com/100-series-disc/p119
The new disc is a different disc, its listed under the 500 series. Link - https://www.mcleodracing.com/500-series-disc/p121
You had mentioned that the original disc said 260531 on the label. Yet you received a 260131 disc which is actually a 100 series disc.
Now you purchase the same part number and actually get a 500 series disc as its supposed to be.
Thanks,
John