A parts house that has access to the Dorman line of products will have a good selection of studs.
Both Caterpillar and John Deere have hardware catalogs with a wide range of high quality fasteners.
McMaster Carr supply has catalog online with many hardware and fastener and supplies-a toll free number for ordering and quick delivery to your door.
Many studs like these have an oversize thread on the end that screws into the casting so it will be retained but a looser thread on the other end to allow easy running of the nut.
But not critical, and many a peice of all-thread rod has been fit and used with good results--it's just nice if the stud stays in the casting and the nut comes off.
