I don't even test those anymore. I give them the boot. I'm pretty close to refusing anything and everything pre-1990. So much easier not having to deal with junk.
This is the factory set up on many of these heavy duty trucks. If it had the emissions label still it would read something like TWC/OC. Some 1 ton trucks only have one cat and it is after the muffler.
If it's the one I'm thinking of, Yep that's where they put them.
I still see those once in awhile. Those old "bead" cats are pretty tough. There's a crazy old man with an immaculate 77 Vette, and he makes early morning appointments every two years so I won't get too much grime on his car while I carefully inspect it. It has the original "bead" cat, and always passes with flying colors.
So , the old trucks with the flat looking cats. that are located After the muffler are okay as long as they don't have one forward of the muffler ?
NO some have one in front of the muffler ALSO (T2) and the emissions label will read OC/TWC.
If you look in the green Mitchell application book for, as example, 1989 Chevrolet P/U 5.7L TBI 8501 GVWR it shows OC,TWC for California only BUT the white Motor book shows one TWC.