I ran a 1999 summit 670x threw the parts fiche and the stock can interchanges exactly with
1999 summit 670x
1999 mx z 670 HO
1999 mx z 670 HO T.H. ( not sure what the th is for )
So to answer your question: Yes the 1999 mx z 670 ho can should fit your sled fine. I would wonder why they do not offer the other model unless the sound levels are not the same.
Nice, I may have to throw down the $250 pretty soon and get the "performance" can for the mxz 670 (my summit). THANKS! And the sound levels ARE different between the 3, heres the cut-paste off the site...
MBRP Stainless Steel Exhaust Silencers
Three choices of silencers to fit your riding experience!
Trail
6" can (body)
*The lowest in weight loss and performance, but provides increase of machine performance with minimal noise volume
Standard
5" can (body)
*Medium weight loss and performance while providing increase of performance over the "Trail" with a noticeable increase in noise volume over stock silencer
*Additional weight is saved by less packing inside the can, increasing noise output
*Heat dissipates faster allowing the machine to run cooler
Performance
4" can (body)
*Highest increase in horsepower and greatest weight loss of the three, while giving definite performance increase over the "Standard"
*Less packing inside can allows for additional weight loss but noticeable noise increase and allows the heat to dissipate even faster