Different size front and rear tires potential problems

I Rally cross my taco, am I'm considering using the stock size tires on the front with larger tires on the rear. I have an X-runner so the rear wheels need all the help they can get putting power down on dirt, but I would like to keep the fronts the stock size so that i don't raise the center or gravity too much.

Does anyone know if this will cause problems with my ABS? the truck is an 06 so there is no traction control and the limited slip is mechanical.

215/70 15 front and 235/7515 rear make the difference in diameter around and inch and a half. and 23575/15 is the smallest size that I can find mud tires in. ( unless I buy very expensive rally tires)