Generally the only time you need primer is if you are painting on bare metal. If all you are doing is painting over old paint, you can do like 87FloridaYJ did and scuff up the old paint and apply a coat over it.
If you do decide you want/need primer, most anything will do but the original for military vehicles was Red Oxide zinc primer.
I'm not familiar with the 30118 shade but I am using 33070 for my Willys restoration. There is a place in Pennsylvania called Army Jeep Parts
that have quite a selection of Gillespie paint.