4th Generation GT suspension question from new poster

[Dave on Smethurst]

Hello all:

I've just bought a 1995 OHV GT, and I've noticed that it's a bit loose in left-right transitions. I realize that the solid axle has its limitations, but I thought that something like a set of Eibach springs from Tire Rack combined with some Konis may button it down a bit. The 245/45-17 Yokahamas seem like decent tires and I'll use them until I wear them out, but I have a chance to buy set of 2012 18" stock Mustang GT rims. I thought I'd run 245/40-18's on the front and 275/35-18's on the rear. I don't want any problems with fit - will the offset on these rims combined with the wider rear tires create any fender or suspension clearance issues? I realize this combination is also likely to create a fair bit of understeer - any swaybar suggestions for neutral handling? It'll remain almost exclusively a street car and long-distance GT, but I may use it for an occasional non-competitive autocross, so I'm looking to build a neutral handler and I'm not interested in sacrificing ride quality.

Thanks for the help,
Dave