Yes they are...input shaft sizes are different, however, as the Cleveland utilizes the big block input shaft. A Windsor can also run the smaller 10" & 10.5" clutch and 157T flywheel assemblies with the smaller 289/302/5.0 bell housing while the Cleveland can only utilize the larger bell housing for the 11" clutch and 164T flywheel. (The Windosr can also run the 164T flywheel & 11" clutch, but with a smaller input shaft).