1964 plymouth Valiant QA1 upper and lower control arms. What disc brake kit works ?

The first choice should be what bolt pattern wheel do you wish to use. That would determine which upper control arm to buy. Big bolt patter wheels you should buy a 73-76 upper arm. Small bolt pattern wheels you should buy an early style up to 1972 small bolt ball joint arm. The small bolt 4 piston caliper Kelsey hayes disc brakes fit the small ball joint. The later 73-76 single piston caliper fit the Large ball joint. Hope this helps. The lowers are all the same.