I looked at that when I put the 330 engine in my MOSE Magnum. There was not exhaust with the machine when I got it and I had gotten the exhaust for the 330. Problem I found was that the mid pipe is different to so not only would I have to manufacture new mounts for the muffler, but it would have to move forward to match up with the muffler. That would have put it too far forward for the plastic to fit.
Another consideration is that the exhaust is...well tuned for lack of a better term....for the engine. The right amount of silencing but leaving the best performance. Not sure a later sportsman would fit that bill. You don't say what size magnum you have but if you get a muffler of the same size displacement it might work.
My 2Cents, it isn't worth the effort for the little $ savings
2001 Magnum 325 with a blown engine; rebuilt 2004. Broke timeing chain 2016 rebuilt again and still running. Warn winch and Moose 60" plow
2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. 12x7 front, 12x8 rear, QSC Clutch Kit
My Trail Machine:
2004 Sportsman 600 Twin, 25" RipSaw Tires on stock steel wheels, Moose rear box
Completed Project machine:
2001 Magnum 325 MOSE with a blown engine. Transplanted a 2005 Magnum 330 engine. Committed suicide on the trail Oct 2016. Spun Rod Bearing after oild cooler line failure. Rebuilding Engine.