Not sure if it has been done or not, but I would guess it would be expensive. You will obviously need the hard parts. Carb, fuel pump and fuel lines, choke cable and throttle cable. But also I would speculate that you will need some different harness parts and at least the ECM.
Has the EFI system changed that much over the years. Would it be possible to use some of the parts from a later model EFI system to make it work? Not sure how long they made the 700. If the hard parts are good, then maybe something from a later 500, 600 or 800 might work.
2001 Magnum 325 with a blown engine; rebuilt 2004. Broke timeing chain 2016 rebuilt again and still running. Warn winch and Moose 60" plow
2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. 12x7 front, 12x8 rear, QSC Clutch Kit
My Trail Machine:
2004 Sportsman 600 Twin, 25" RipSaw Tires on stock steel wheels, Moose rear box
Completed Project machine:
2001 Magnum 325 MOSE with a blown engine. Transplanted a 2005 Magnum 330 engine. Committed suicide on the trail Oct 2016. Spun Rod Bearing after oild cooler line failure. Rebuilding Engine.