Cats aren't available from previous owner. Local muffler shop wants almost $600 to install mini cats. This car sounds amazing I'd hate to dump cash into something just to get a sticker this is a joke
If your rear O2s are turned off, then I don't know of any way that you will pass. I think you will have to re-tune at a minimum.
I think you are allowed one and only one readiness monitor to read "not ready" and still pass, but it cannot be the catalytic converter monitor that fails. That one has to be "ready".
Even with your rear O2s turned on, I don't see how your car will pass emissions with no converters. Once they are turned on, they will notice that the converters aren't working (since they are gone), and they will turn on the CEL, which will fail your emissions test.
So I think you really need both a retune and catalytic converters.
Also, a word of caution - aftermarket 49-state converters have the bare minimum of precious metals in them to work for a short time. They are way less robust than OEM converters, or even California aftermarket converters. That's why they are less expensive. So it's not really guaranteed that the car will pass with them, though it might.
The safest thing to do would be to buy a used OEM set, but they are hard to find. They run $400 - $500. Then again, they wouldn't fit your long tube headers anyway. So you would have to get rid of your headers as well.
Speaking of the long tube headers, they technically should cause your car to fail a visual inspection, even if you have working cats and a retune to enable the emissions equipment. So even if the CEL stays off with all the new parts, you might still fail. The only way around that technicality that I know of is to buy parts that have a CARB Exemption Order number, but the only headers I know of that have it are shorties. You might be able to get around that if the shop is not extremely diligent in the visual inspection, and if the car passes its own self-test.
So it looks like you are into about $1,000 and a little luck to pass. If you sell your long tubes, you might get back a few hundred toward the new emissions parts, and it will eliminate the luck part.
Or you could sell your car out of state and look for an unmodified one.
I hope the original owner got a nice payout for his original converters. He should have asked for at least $300.