Heres a good link describing how some of the following components can increase downforce and help "increase" front tyres
grip while others can assist with aerodynamics.
Front Wing
Carnards
Front Splitter/Air Dam
Rear Diffuser
Chassis/Under Body
Side Skirts
Vortex Generators
Rear Wing
Spoilers
DRS/ Drag Reduction System
http://www.rapid-racer.com/aerodynamic-upgrades.phpone of the issues will be custom making these parts as they are not off the shelf items.I.e the underbody.But items like rear spoilers are widely available.