That links shows/explains a Chevrolet-provided technique/bolt for " . . . using 1958 or earlier rockers on a 1959-62 engine".

Does your bolt have a hole in the bottom (see attached images)?

(images take from Pre '68 Dave's excellent blog site - at the link in an earlier post in this thread)
Attachments
drilled head bolt 100_1913.JPG (21.76 KB, 141 downloads)
drilled head bolt 100_1912.JPG (34.67 KB, 141 downloads)