I do believe, that the 1981-current CV/GM's have the same shaped exhaust underneath. At least, where they run from the 'X' pipe to the back bumper anyways.
I found a used set of flowmasters (40 series?), and put them on. The pipes on my car were offset as well, but you'll find that on most cars. So any muffler you pick up, make sure it has the right offset for your car.
I really do like the sound that the flowmasters give off, you can actually HEAR my car now when I'm stomping on the gas
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