I don't know for a fact, but I think the chassis are very similar with the Cadillac with possibly a longer wheelbase. The Chev. manifolds are most likely the same, so it should fit. Did the Cadillac have dual exhausts originally?
The '94 Caprice I had was the small L99 4.3 engine. It had single exhausts with a Y pipe. It might have been smaller diameter and might choke a 350. The car needed an exhaust system and a manifold bolt broke in a hard to access point. I kept the drive line and scrapped the car. It had seen a few too many winters anyways.