Brake drum question

[cpldale]

I bought what I was told were 46-48 front and rear brake drums with hubs. The drums were out of spec so I used a 5/8 hole saw to remove the the studs and separate the drums from the hubs. So far, so good. I went to order replacement drums and realized the center hole in the replacement drum is 3 1/4". The center hole in the old drums is 4". Not sure what I have. Any thoughts?