Manual drum master cylinder

[69SCSS]

Hey guys, I'm probably going to have to go with manual drums for the time being on my truck due to my budget, but i wanted to find out something about a difference in the 2 cabs I have had. My old cab (a '69) had only the hole for the pushrod and had manual brakes. The new (to me cab, a '68) has a hole for the booster lever also. There are 4 bolts on both. Is there a plate that covers this area on manual trucks? My old cab was solid in that area. I've attached some pics. I couldn't find anything on the LMC site or anywhere else.

Thanks for the help.