Here is a word doc with a pic of the spreadsheet in it. The puch manual lists the engine gear ration as 5.05:1 and chain ratio refers to front sprocket x rear sprocket. I measured my tire diameter to be exactly 22 inches (pretty damn close anyway) and used 3.14 for the circumference to figure out how far I went with one engine rotaion then multiplied it by the rpms to get final speed.
To get a speed of 38mph with 14 x 45 setup you'd need 9500 rpm. what carb are you using to get this? How fast can you get a non-ported metra to turn?