In order of the yellow circles (left-to-right):

3/8" NC 16 Grade 5

2-3/4" bottom of cap to end of bolt (1949 - newer)
1-11/16" unthreaded shoulder
I don't have a 1948 and earlier engine so hopefully someone else can provide the length.

1-3/8" bottom of cap to end of bolt
1/4" unthreaded shoulder

1-3/8" bottom of cap to end of bolt
1/4" unthreaded shoulder
Attachments
Manifold Bolts 01.jpg (37.93 KB, 109 downloads)
Manifold Bolts 02.jpg (82.09 KB, 109 downloads)
Manifold Bolts 03.jpg (51.96 KB, 95 downloads)

Last edited by buoymaker; 05/24/2022 3:31 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."