Probably Speedway plus a lot of others. Be sure the adapter they sell you doesn't just change the pattern but also has the step up to allow for the raised area on the 1928-35 drums. If you don't understand what I mean about the raised area see my earlier post on a slightly different topic http://www.jalopyjournal.com/forum/showthread.php?p=8330045&highlight=stephens#post8330045
Lots of adapters on EBAY around $60 a pair last time I looked.You'll need 1.25" thick ones.The step support plate is sold by Mac's.Rally America I heard does an adapter with the support ridge.