They may have been what we now call grade 8 bolts. I don't think you could go wrong
using grade 8 bolts to bolt the backing plates and control arms to the spindle.
McMaster Carr
Grade 8 Cap Screw,
Length 3 1/4",
Thread length 1 1/4" to 1 5/8",
5 to a pack at S8.36
Part number 91257A745,
They also have the short upper ones for the backing plate to spindle if you need those.
Denny Graham
Sandwich, IL
