Any M5, M6, M7 tunnel will be the same... as long as it is a 141". The M5 only came with a 141" as I remember? I'm assuming you could use any of the above for you project? Got to be a few out there for sale. Good luck.
I'm quite sure M5's were 141". I know that in 05 and 06 the M5, M6, and the M7 were available in a 141" track. I think you meant 141" There has to be a lot of parts out there as these sleds have been around a while and sold like crazy. Have fun searchin