The backcountry 1.75" will be a good choice... About $620 delivered in USA
Other great choices are 144" series IV Polairs and the 15" wide 2" tall ski doo 144 from the 2003 and earlier ZX summits... both are 2.52" pitch, both work well on groomers with scratchers (even better if you run all the bogies on it in marginal conditions)
Lots of 2009 800 shifts out there with tracks changed out.
The same series IV, [Part #5413073] 144 x 2" x 15", 2.52" pitch track came on:
2009 800 & 600 144 shifts
2008 600 144's
2007 600 144's
I believe these are a mixed durometer track, a bit stiffer than the previous years.
Series IV 144" X 2" from a 2006 144" standard (non snowcheck)
PN 5412888
Series IV 144 x 2" from 2003 to 2005 edge chassis
PN 5412242 (superseeded by 5412888)
You can usually find great deals on these used or take offs.
A Camo 9875 Challenger 144" x 15" x 2", 2.52 pitch, fully clipped is $620 (similar to the Ski Doo ZX track)
As for moving your rear axle back...an offset big wheel kit would help you take up some of the extra slack. I don't recommend bigger than an 8" on the stock rear suspension as lager will lift the track off the top idler under full tail compression.
If you still want stellar on trail performance.. the rip saw lite 1.75" is the way to go, but as said above, you will need to switch out drivers or find a complete take out driveshaft from a 2007 and up Dragon RMK
A 144", 2" tall finger track would work well in all but the dryest powder (still better than most 1.75" tracks" ... hook up really well on hardpack and spring conditions.
I'm not sure who makes the non extrovert drivers for the 2.86" pitch tracks on the tubular drivshaft in your Switch
The bulkhead cooler is the same part # on the 600 RMK's and the Switches in 2006, so clearance in that area should not be a problem.
Just my 2 cents