1/5 scale conversion & cheap are not two words that go together...
With a little bit of maths, you need to figure out two things:
Select a motor that spins at about 20-25,000rpms on your desired voltage
Select a motor that produces about 4-5 horse power on your desired voltage.
You will also need a suitable esc that can handle the large voltages.
There are a few 1/5 scale conversion threads around, so enjoy the reading...
