Bushnell makes a some what inexpencive radar gun for $99.99 shipped and it is designed for sports and R/C.
That would probably give you the right MPH or KPM depending on were you live. My local Hobby Shop/Raceway is getting one soon, hope to see what my K3 really does. This might also help with my setup changes. I think I might just buy one so I can do speed runs down my street and on the off road track. hhhhhhhhhhhhhhmmmmmmmmm I guess I know what to put on my X-mas list.
Most buggies out the box will at least do 40+mph but it is all about motor/pipe combo.