Jason : After a little "digging" (I.S. Sheet 1295, 1965 MPC, 1966 MPC, 1960-66 MPC, and AMK's "Guide to Fasteners"), I believe I have some answers for you ; at least based on these resources.
First, and interestingly, none are shown as the "theft-proof" type, although whomever added those was probably smart to do so. Using the resources I noted, here is what is shown :
High Profile - 2, # 54448-S, #10-24 x 5/8", Hex Head, Gr 2, Split SEMS screws
Low Profile - Wire Cover - #52718-S8, #6 - 18 x 3/8", Phillips, Pan Head, Self-tapping screw
Bracket - #379773-S8, #10-24 x 5/8", Slotted, Fillister Head Shoulder Screw, with 1/2" threaded
What I think may be a mistake is the finish on the bracket screws for the High Profile Rally Pac, which are shown as "plain", as opposed to those on the Low Profile Rally Pac, which are noted as "S8", Zinc plated.
Pictures of the 3 screws are attached.
Hope this is what you were looking for.
Bob