It seems that studs/nuts are the fastener of choice for high steer arms to FT knuckles. Why wouldn't grade 8 bolts be just as good?

because when you tighten down a bolt it stretches the threads and puts all the stress on the threads themselves. when you use a stud, with a tapered nut, it puts the pressure on the arm that your tightening to as well as the nut itself, both of which have more meat to hold to. basically the more you tighten with a stud and nut, its just doing exactly that, getting tighter. the more you tighten with a bolt, it stretches & gets weaker and can loosen in turn then breaking.

most of the steering arm bolt failure happens because the bolts have worked themselves loose, and then end up shearing.

because when you tighten down a bolt it stretches the threads and puts all the stress on the threads themselves. when you use a stud, with a tapered nut, it puts the pressure on the arm that your tightening to as well as the nut itself, ...

I'm using Blue Torch Fabworks arms with the tapered (conical) washers. Does the same theory still apply if you are not using tapered nuts?

I'm using Blue Torch Fabworks arms with the tapered (conical) washers. Does the same theory still apply if you are not using tapered nuts?

yes, same principal..