For suspension bolts n Nylocs, I always get the yellow/chromate? ones. I also try and get the higher torque ones if available in yellow and not black.
For non suspension I buy A4 or A2 stainless fasteners.
I use workshop manual for sizes or Canley Classics. (Sorry Dave).
I don't use the recommended wishbone bolts as the un-threaded part is too short; One reason the kits are not a good buy.
Can't remember where I got my yellow fasteners from at the moment.