Screws required to secure the convertible top frame to the inner body structure are not listed in the Service Parts List. These will be one round head and two flat head screws each side. Originally Phillips slotted 1/4-28-UNFx3/4 pointed body screws (zinc plated), because they go into floating captive cage nuts in the body (hidden inside the B-pillar).

(2) PPZ0412 - Pan head Pointed Zinc       1/4-28-UNFx3/4 (round head)
(4) CPZ0412 - Countersunk Pointed Zinc 1/4-28-UNFx3/4 (flat head)

During assembly of the vehicle, the tapping plate for the door latch striker plate attachment must be installed first in the vertical slot. Then the rear kick panel is installed with multiple tapping screws and finishing washers, and the top frame is installed last. That means you must remove the top frame any time you might need to service the rear kick panel or the door latch striker nut plate, or nuts for the cockpit rear corner trim roll, or bolts for the rear wing attachment (replacing fender piping) or bolts for the splash panel forward of the rear wheel. So, the top frame may need to be removed more often than you might think.

These screws and nuts are commonly rusted in place, so the fasteners may be damaged or destroyed in process of removal. If the captive nuts rotate in the cages, you may have to grind away the screw heads to remove the top frame. There are various ways to repair the damaged captive nuts. You can cut and weld in a replacement sheet metal panel with new cage nuts. You might weld in a heavier steel plate with tapped threads in fixed location (being careful with good alignment). I once opened a "door" in the rear side of the B-post (three cuts to bend open the door) for access to the hidden cage nuts. Then bend open one side of the cage to remove the damaged nut, install a new 1/4-28-UNF square nut, bend the cage side closed, repeat for up to three cage nuts if required, then close and weld up the door.

Considering how much pain it is to repair these captive nuts, and that it may need to be done again if more than a few years since the last time, I highly recommend using stainless steel screws (and always use anti-seize compound on the threads). Also hex socket drive screw heads are good for a better purchase with a hex key (Allen wrench) for next removal (unless you want concours originality). Similar flat head screws are used for door hinges (32) and latch striker plates (4). Maybe buy a box full (50) of these screws (in stainless steel).