The reason for different engines, transmissions and drive axles was that they would run one supplier up to the credit limit then move to another until they were at the credit limit and so on, they would then pay the first supplier and then it goes on!! This is why all Boss machines had a works order number so you could trace back the build sheet. I dealt with Boss for many years and I could write a book on stories from the factory, including the day Snivel sacked the milkman!!