Here's a pic of two 99 receivers, the top is a 99-C and the bottom a 99-DL, both have the tang safety. I want to mount a receiver aperture sight on the 99-C, and need some advise from you folks knowledgable on that subject.

Q1: From searching the internet, it appears my only site option is the Williams FP-99S. I can't determine that Lyman even makes a sight suitable for the 99-C, is this correct?

Q2: Both receivers have a screw near the rear of the receiver that I think is called the sear screw, but the 99-C in the top picture has an additional screw head at about the 10 o'clock position from the sear screw. Is that used to attach the receiver sight?

Q3: Does the receiver sight use the scope base screw holes in the tang?

Thanks for your help!!