hallyushows

ng, I already have Sunggyu High Society, but not in avi. just HQ mp4 (47m34s). I downloaded it from dailymotion.. I was wondering if I can do the subbing from there... the video plays from the words "모두가 떠난"

Yes, you can certainly use your own. You can even time with that video, but please start with the part where the screentext says: "특별한 오늘." This come about 30 seconds after 모두가 떠난.
Don't worry even if your timing would start as "0.30..." instead of "11.09" because I can shift your whole part by 11 minutes or so to make it fit into this video.

P.S.
Please sign up using this format

Part:  (ex. 40.00~END)
Position: (ex. Translator, timer, typesetter)
E-mail:  (ex. hallyushows@gmail.com)

Then I'll leave your name up on the main post.