Another possibility is to use a stud that is threaded on both ends like the ones used in a high performance head. You would have to make sure the stud works with your rocker arms and thread the hole in the head. You can use studs that came with the 289 High-Performance heads or Chevy LT-1, #397446.
By the way is that 289 head on a 302? A quote from one of my engine books by Pat Ganahl about using 289 heads on a 302.
"Some 302 engines built before this date", 10/21/68, " used .060-inch thick valve stem caps on the exhaust valves. Supposedly, the longer stem length was required for clearance with rail-type rockerarms, though rail rocker arms were introduced over two years before this. The main point is that there is a difference in pushrod lengths between the two engines, and the problem arises when the long pushrods (302) are used with short valves (289) and stock rockerarms. In such a situation the rocker arms will bind on the studs at full lift, often breaking the studs. ---- The solution is to install shorter push rods to correct the rocker angle." So the way I understand him is if using 289 heads use 289 pushrods.
He also says that the ***** in studs and guide plates are necessary if a high performance cam is installed.
If you want to read more about this get the book "Ford Performance, by Pat Ganahl". Most book stores have it and it is also available on Amazon.com.
Hope that info is helpful.
Good luck,
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