Honda-SOHC

i think my coils are gone on my cb550f
 its not firing on no4.. then after a bit of messing it works!
 but not on 3 .
after fixing that, it stops on 4 again . i have changed the plug caps .but with no luck
i think the coil leads are nackered. and that means replaceing the coils.
apart from  some outhere cb550f coils . are they any outheres that will work well ? or better
 the way they mount to the bike doesnt matter as i have these ones on a box behind the forks  justas long as the leeds arnt two short

aftre this i still have to ballance the carbs and sort out the timeing . im not shore what im doing there either .  one step at a time thow

any one know what the Ratio is for the rev counter / speedo ?
is it going to matter massivly and low speeds [under 60mph]

the frount brake was seased when i got the bike  [was all in boxes mostley] but now have it working . 2 questions

1: is a single piston brake made back in 1977 any good? to toady's standards / should i be looking at  using a more modern twin piston system, and make a bracket out of alloy fit  the unit to  the forks . thinking about using maybe a gs500 st up or a ntv650

2: if i use what i have [it seams easier] how does the brake light switch work .. by manual doesn't say a lot about it . i dont have any leads or what looks like a switch coming out of the master cylinder.  i have no idea how it used to work back then ..
is its easier i could use a master cylinder off a newer bike . but would need some ideas on master cylinders  eg the  master cylinder of my ntv650 might be designed to push more brake fluid then the cb550 one as its set to move a twin piston type ./ might brake the seals maybe in the brake piston  ?