I live in California and was wondering... since my dad mentioned his old buddies used to do this. Since my car is old enough it doesn't have to pass smog. So does it really need the catalytic converters?

Seems every year, there is a push in CA to amend the laws to require cars to meet original smog standards back to 1966. Rumors and news of these attempts cause panic for folks who stripped their smog stuff. Not worth the aggravation, in my opinion. And, if those proposed laws ever pass, then you're really up a creek.

Your 73 model Riviera had a catalytic converter? I thought no car used these until the 1975 model year.

the car is 30 years old. like as not it's been through a couple of mufflers and had a cat added on one of the changes by one of the fine upstanding, law abiding CA muffler shops.