In reply to my own question. From the M&StL 1959 Freight car diagram book. Cars with A-3 trucks were:
Box car 2800 blt 59 100,000 lbs
Box car 2500-2502 blt 58 100,000 lbs
Box car 2700-2706 blt 59 100,000 lbs
Box car 2000-2058 blt 57 140,000 lbs*
Hopper 66001-66499 blt 47 140,000 lbs*
Hopper 66501-66999 blt 57 140,000 lbs*
Hopper 67001-67063 xC&O blt 56 140,000 lbs*
Covered hopper 70201-70279, 70301-70599 blt 55,6,7 140,000lbs*
Covered hopper 71001-71039 blt 58 140,000 lbs*

While I have display models of all these cars the only one I run is a Stewart hopper from the 66001 series. So, I guess I'll need a pair!

From the CGW 1968 diagram book:
Box car 15000 series blt 66 137,000 lbs*
Box car 300-349 blt 55 140,000 lbs*
Bulkhead flat 3001-3010 blt 59 100,000 lbs
Auto rack flat 3500-3504 blt 61 120,000 lbs
Auto rack flat 3505-3507 blt 63 120,000 lbs
Gondola 1351-1355 blt 62 140,000 lbs*
Hopper 6000-6099 blt 57 140,000 lbs*
Covered hopper 761-770 blt 59 140,000*
Covered hopper 7101-7105 blt 64 190,000

Did I miss any?
Clark Propst