I'm finding that these conversions are not so cheap!
For the Hen Long/Dickie tug I mentioned in another thread- only US$50 landed at my door, then:

$40, used TQ3 27 MHz radio (proportional, 2 1/2 ch)
$20 NiMh battaeries
$12 new washer pump
$40 Mtroniks ESC
$10 steering servo
$15 servo & relay for pump
$20 paint & decals
$20 various wiring plugs, terminals

Total add- $177, on top of the original $50!