I'll be glad to help, but I'll need a little info.
1. What engine are you running?
2. Do you know what brand pressure plate you have?
3. How much horsepower do you have?
It's true that the 1-1/8x26 input shaft size is a GM size, but you don't necessarily go searching for GM applications when looking for components. A NAPA disc will be organic on both sides, so depending on the pressure plate, it may or may not meet your horsepower needs.
Feel free to email or call:
brent@b2motorsportsllc.com
502.759.1431