i have switched several flywheels from v8s to inline 250s and 292s with no problem. i am not very familar with the v8 ones, but i think there are 2 main sizes for the inline sixes. i always use the large size on my 250s and 292s. the one in my 63 was the original one off the 327. it was the same size/ same teeth. there is a change in the flywheel to crank bolts size in the early 70's. if your flywheel has the larger holes i think you can get bushings to use smaller bolts but it's easier to just get the flywheel you need. i also have always used the heavier duty clutch and pressure plate. i bet someone will come along that knows more than i do. good luck, hr