Modern Musclecar used to sell a Y-pipe kit for the Hooker longtubes mandrel bent 3 tubing with a Flowmaster 3 Y to merge them together. You can have O2 bungs welded on for the O2 sensors & you can get the O2 extension plugs from Casper Electronics I think they sell the O2 sims as well if you need them. You can also mount the O2 sensors after the colletor in the Y-pipe without any problems.

I passed emissions running the Hooker longtubes with the CC305 cam Crane Gold 1.5 intake rockers 1.6 exhaust rockers.

I DID have to use a catalytic converter to pass emissions though just rigged it up to get through.

First time I tried to go through engine loping no air tubes on the headers air pump gone no cat what so ever the inspector made me pop my hood and called over a supervisor! They put me on the rollers and I got something like 8XX PPM of whatever was suppose to be like 200 PPM max I failed the inspection and the test of course.

After putting the cat on there I passed the emissions test no problem. You could now easily breath the exhaust whereas before pedestrians merely passing behind the car would tear up from the engine running so rich at idle from the cam and no cat.

The longtubes sound sweet too if you get them Id recommend getting them coated uncoated headers will eventually cook everything that passes anywhere near them namely the ABS wires on the passenger side and the A/C box on the firewall toast.