Sorry, but I have to vote that it would be foolish to do that. Ride the 900 as is. That's got way more power than your 700 has. Make sure you have both SLP torque arms in there, make sure that the clutches are aligned, and make sure the other stuff you have to do has been done. Ride the 900 and laugh at all the people that say it is junk. Tell them you only paid $3,500 for it, and then kick their ass right up the nearest chute!
2001 RMK 800 151"
1990 Indy 400 (Slightly modded with welded tunnel cracks and various used Indy parts from models throughout the 90's)
2006 Stihl Chainsaw
1980's Vintage Lawnboy Lawnmower (3 in collection)
2005 Husqvarna Weed Whacker (It sucks to rewind the string, but that 31cc motor sure is torquey!)
2000 Polaris XCSP Edge 600 (1.5" Track, 22 40 gearing)