>>28455754 (OP)Top speed is a function of CDa times peak hp, with some fudging up or down due to gearing(you want the car to top out right as you hit peak hp in top gear). Aerodynamics is a big part of it. Look to standing mile and I hate to say it, but hypermiling builds. Undertray, splitter, moon discs, ect. The next two questions you need to be honest with yourself about are what is your budget, and what is your goal that you'll be happy with reaching?