Ok let's settle this...
The following info I have taken from rockauto.com from the two different size flywheels they sell for a 250 straight 6 in a c10
The 153 tooth flywheel for use with the 10'' clutch
Pressure plate bolt circle: 11.626''
The 168 tooth flywheel for use with the 11'' clutch
Pressure plate bolt circle: 12.625''
https://www.rockauto.com/en/catalog/...,flywheel,5348
So short answer: No the 11'' clutch and pressure plate will not work on the 153 tooth flywheel.