If you look at the spread sheets here...
http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html#Drag%20Force%20--HP%20to%20run%20a%20Speed....you will see there is one called "Drag Force-HP-Thrust-Weight". That spreadsheet will figure the Drag Force on a vehicle, the HP needed to run a certain speed for that vehicle, the thrust and the weight needed on the drive wheels for a given thrust and speed.
I also just finished a spreadsheet that is mainly for lakesters and figures the HP needed for a speed based on Cd and frontal area of the car and of the tires/wheels separately. Since the body can have one Cd and the exposed tires/wheels another it figures them independently and then combines them into one HP total. I don't have it up on my site yet, but if there is interest in it I'll put it up and a link to it. Cars or streamliners could also use it, just don't fill in the section on wheel/tire diameter, width and Cd. It is based on the formula in one of the spreadsheets on the page I posted a link to above, but is easier to use I feel.
If anyone is interested I'd be interested in comparing the spreadsheet output to real world experiences with cars that have some known data,
Sum
