Yes, an additional jamb anchor can be used at the bottom of the frame in lieu of the typical (adjustable or weld-in) base anchor in fire rated frames.
This is limited to the anchor designed for...
No, an adjustable base anchor is not supplied on frames with existing opening anchors.
The anchor design for use in existing masonry walls, is a pierce and dimple in the frame soffit for 3/8"...
See below for commonly requested dimensions on the MA lock. Dimensions not found in other literature have a square around them.
CL refers to "Centerline".