You can also use the direct drum from an A518 and use the standard width clutches. There's a seller on Evilbay who sells remans LOADED with new clutches for 20 bucks and 12 bucks shippin. Just search 904 drum and you'll find it.
you better check what year your trans is before you go buying A518 drums,,,,,the 518 is based on the 727...the A500 (42RH and 42RE) is based on the 904...some of those drums have two bushing...alot of the older 904 front drums have one bushing...
the 5 disc drums that i have both hit my pump and did not seat ...tried that last week...even posted pictures ....so buyer beware...
here is one of the pictures...you can see the drum on the right which is a 5 disc 904 drum how the inside is recess...the outer area hits the pump before that recess area seats on the pump....there are pumps that are available for those drums...dont mix and match parts unless you know what you are doing....