4 speed flywheel

easiest way to tell an externally balanced 360 flywheel from a 340 unit, look at the counter-bore holes in the back of the flywheel, 3 holes=360. 2 holes=340 (external) no holes= neutral. Ive been told that 340's are whats called a "detroit balance" meaning the entire rotating assembly is balanced as a unit. so some flywheels accordingly are balanced to a specific rotating assembly, and may not work well with other units. hopefully someone else can back that up.