Hmm. I was going to suggest a square set up as well, but really in order to keep tire size and compound a
constant more than to play with relative grip -- a lot of that will depend on alignment settings and weight distribution/suspension more than anything.
I guess you could buy ultra sticky fronts relative to the rears, but that sounds like it will just make the car unpredictable...
So, assuming equal sized tires of same make, you want to stiffen up the rear relative to the front. That means a beefier rear anti-sway bar and firmer damper settings in the rear and softer in the front, if you can adjust them. Any other bracing you can add to the rear (without adding significant weight) will tend to nudge you more towards oversteer.
I think, maybe a little more camber in the front relative to the rear will help tuck the nose in too... not 100% certain on that one off the top of my head.
Scan over this site for lots and lots of advice on setting up cars for road racing
Autocross to Win (DGs Autocross Secrets) - ATW Home Page
This thread is helpful too
Suspension adjustments and how they affect handling