You can use a piece of allthread rod , probably 1/4 x 24 coarse, cut to the right length. Nobody will see it anyhow, since it is hidden in the air cleaner
I've used standard coarse threaded rod... I believe most carbs have 1/4" x 20 threads in the hole for the stud... Then I just use the standard 1/4" x 20 wing nut for the air cleaner....
