Yes, they are different. If your looking for a base to copy off of for a US version then the bulgy seems to be the one. The gas port is in the correct location so there is no need to cut down a gas tube to fit as you would need to do with a Russian one. I don't have much info on the yugo ones but akblue has more info on this subject that I do. Hopefully he will chime in soon. Or you could pm him.
As far as producing them you could do it a couple different ways. Having worked in a steel foundry in my youth you could make a mold out of silica sand if you had a FSB to pattern off of. After the initial part is pored With molten steel then the final machining can be done.
Or you could machine one from a lathe/mill which is what a lot of people/manufactures do. Then heat treating the part afterwards is a typical process.
The later process is the gererally most cost effective if you plan to sell to a small market. However if you were to set up a small foundry in your garage or shop then it would make production easier if the product were a hot seller.