Legally, yes. Functionally, no.
Yes, it has a catalytic converter.
Gas engine, yes.
Yes
Yes, it most certainly does. In fact it is illegal to remove the converter.
The install is the same as a muffler. A muffler shop can do it cheaper than anyone else.
It has two cats. Both under the cab and the muffler is under the bed of the truck.
If it doesn't now, it did when it came off the assembly line. They were required as of the 1975 model year.
I own one. You can ask me or search forums like truckforum.org. What exactly are you wanting to know about them?
a 1984 buick century weighs about 4,000 lbs.
Clogged catalytic converter will do exactly this but failing oxygen sensor could cause it too. Most probable is cat converter.
check state laws is different state to state usually below 8500gvwr yes above no but again check with your state
4.75