There is a bolt that holds the wheelhouse to the fender just behind the top center of the wheel opening. It is often the place where dropped cars rub the fender. The drop spindles move the wheel out about 3/8 of an inch.
On a further note, You should check your shock end to ground clearance with the 15 inch rims. The prior owner of my wagon had a flat, and the shock hit the ground before the rim...it severely damaged the suspension arm on that side of the front, as well as bent the wheelhouse at the back. The easiest way to check it is to put a bare 15 inch rim on one side of the front, and allow it to rest on the ground. If the shock hits first, you have an interference issue. With the drop spindles, you may be able to jack the rear corner up, and the front may come off of the ground before the rear, if the jack will not fit under the frame at the front (I would be careful using the tire change jack for that purpose...you will be lifting 2200 lbs./1.1 tons).
As far as tire size, I used a 215/70/15 on the front of mine with 255/60/15s on the rear, and had little rubbing after removing the above mentioned bolt. The issue with front tire size vs. rear ones is that you can disrupt the antilock sensor outputs.
Since the wheel is moved out a little, you could get a wheel with 3/8 inch more backspacing, to bring them back to the original position. You could then use the original size tires. Before you do that, make sure the shock ends have clearance. I changed to 17 inch rims to solve that problem. I am running 255/50/17s on the rear, and 225/60/17s on the front. I have only heard it rub twice so far. I am considering 235/55/17s for the front, because they are the same diameter as the rears, and I can use one spare for any corner. These are all 27 inch tires. A 235/70/15 is a 28 inch tire, and swapping to the smaller 255/60/15 will change your speedometer reading, and you should change the computer reference for the different tire to correct it. A 255/55/17 would be a 28 inch tire, but only one manufacturer makes them...Bridgestone. A 235/60/17 is also a 28 inch tire.
As a last resort, you could do the old school baseball bat clearance method, where you allow a baseball bat to roll between the tire and fender. You have to be careful, because it can bend things you do not want bent, and you have to do both sides the same. Should you ever need to change wheelhouses, or fenders, you would have to reroll the new parts to match. Again, check your 15 inch rim shock to ground clearance before doing anything.