Two Different Types of Brake Drums

Dear All
I have a 67 Plymouth Valiant Signet. I found out after taking the front tires off, that there two different types of brake drums. The drivers side is a typical drum that goes on over the studs. The passengers side has the type of drum that has the studs on the drum. You have to remove the nut and cotter pin on the spindle. I don't think that it would have been built at the factory this way, so maybe through the years somebody changed one of these spindles. It has the 9" brakes.
I want to replace the drums. My question is, can I find a drum with the studs attached, or are they fairly easy to install. I don't want to get into changing the entire back plate and spindle, and all other necessary parts. It works as it is, but where or how can I get this drum. I'm sure that somebody out there knows. Maybe it's easy. Please help. Thank you.

jimmys67