Alvin, could you sneak a picture of those "bushings"???
I've never seen a bushing in any Stovebolt exhaust manifold
heat riser bore. All of them that I've run across simply had
a hole drilled thru the casting and that is usually what
ovals out.
As far as repairing it, as Mike has posted, the fix is
normally to cut out the old shaft, ream out the hole to
take an over-sized shaft (available from vendors).
Timing or alignment of the the slot, butterfly, weight is
the difficult part but is critical to the heat riser working
properly.
Denny Graham
Sandwich, IL
