Thanks for the quick answers guys
I'll probably end up going 52:18.

Also, i measured my rear spacing and it turned out to be 125 or 126 mm (It's an old Miyata frame)
Will i be able to put a rear wheel spaced for 120 mm?
I was reading around and found a topic on here with someone trying to do the same and they mentioned bending they stays ?
Would I need to go that far?