Can i convert a road bike to cx?
 

I have a old schwinn varsity sitting in my garage, can i convert that sucker to a cx bike? Im looking to do some trail riding and a snow bike.

new fork with brake mounts? how about the rear?

a new fork w/canti mounts should solve your problem in the front, but you could have problems with both tire clearance (of the frame) and mud/dirt/snow/gunk clearance if you are using a standard road brake on the rear.

Changing the fork into a CX fork will change the whole geometry of the bike.
A standard road fork is 374mm compared to a CX forks 395mm.
Could be a good thing looking at the head tube angle, but bad for the seat tube angle.
All of a sudden you'll be riding a chopper.

Start out slowly, begin by putting on some cheapo CX tires and see how it goes. If the bike holds up, then put more stuff on according to what you feel you'll need. If the whole thing falls to pieces, however, then just go out and indulge yourself with a brand spankin' new CX bike.