It sounds like you may need to adjust your fender up to close the gap. Lay a level across from one fender to the other to see if they are on the same plane horizontally. Do this as close to the firewall as you can. Also check the level of the core support. If both the fender and the core support are off bubble the same amount you will need to shim up your core support. If you have not already done so check the core support where it attaches to the cross member to see if there is any rust rot causing the problem.