How could i go about removing Velox Camber Plates mounting bolts?
 

I'm replacing them with longer bolts for use with the Subtle Solution 1" Aluminum lift kit.

Those aren't bolt, they're studs. I have no idea why you're doing a 1" lift on your car, but FWIW, you can get these out with a shop press. You should heat them a bit with a torch beforehand, but not too much, remember you're working with aluminum.

Subaru rally life me thinks....

If you don't have a press, Bubba says you could try putting two nuts tightened together near the top of the stud, then (as @Tristor suggested) gently heat up the plate (only) with a torch, then rap on the top of the stud, where the nuts are, with a hammer.

humfrz approves of Bubba's suggestion (this time).

Put a socket under the stud head (so it’s touching the camber plate only) and then give the other end of the stud a good whack with a 3lb hammer. I’ve done that on plenty of aluminum coilover top hats and they’re fine.