Re: I bought a virtually new bike
there is 4 mounting studs. 2 on the back. 2 in a bottom/forward position.
replacing them is a good idea. many of us re tap them for bigger studs.
your calculation is correct. i double checked w/ google.
if you put in part of an equation or a conversion. it will give you an answer that isn't a website.
if you can get the studs off w/vice grips go ahead.
a better way is using 2 nuts. put them both on the stud. tighten them together. then unscrew with the nut that is closer to the engine.
i haven't the need to touch my head bolts yet. i imagine i will need to one day. so you can either do it now or later.