I've been keeping an eye out for sled deals around my parts, and they just aren't out there. Prices have been up since the long winters, but the sleds aren't getting any newer or nicer.
I was pestering some dude today about a 1992 Formula MX 500 (470 Rotax). Guy is asking $500 and claims its running, but in the pics he sent me...the oil pump is not connected to anything nor blocked off, the throttle cables are totally shot, everything is grimey, no airbox, wiring has been messed with, leaves & stuff in the
Engine bay meaning she's spent quite a bit of time stored outside, claims 120# compression is "fresh", etc. Plus the hood sucked and its effing JULY with a forecast temp of 93F (LMAO!). I actually offered the guy $180 cash, and he declined. But that's Craigslist for ya'!!

Buy a running sled which will include the wiring, rectifier,
CDI (Capacitor Discharge Ignition), coils, fluid tanks, gages.
Sell the sled roller to recoup $'s.
Buy Farr's mount plate kit UNWELDED.
You can weld the mount plate and do the exhaust header mod with some elementary welding skills & some time.
You don't need the piece of armor Farr provides in his kit. A simple piece of bent tube would suffice (Rotax recoil cover clearance).
But if you're in a hurry and/or don't have the skillset or confidence, Farr's kit does the trick.