[Ashlandchris]

Rc10 is still a quick car, although if this is an 1989 version it might be better to save as a vintage and getting even a low cost more modern version to use in the rough and tumble of day to day racing.
Sensored motors have a separate lead between motor and ESC and it makes the power delivery much smoother as it constantly communicates.
I did have an unsensored Orion which was almost as smooth, but also had an unsensored leopard cheap ESC and motor combo which was rubbish and would "cog" all the time (car doesn't seen to want to set off without a kick). I'd always recommend to go Sensored simply for the smooth acceleration.
I use speed passion stuff and it is great. There is cheaper available and also pricier.
If putting modern electrics in old RC stuff, don't be tempted by power - I'm told one can mess up an old gearbox quite quickly with a hot motor. 10.5 turn should be as fast as I'd go. I have an old original optima which I limit to 13.5 turn as there is no slipper clutch to protect the gears. Don't know if '89 rc10 has a slipper?