I am not stocking many new engines currently, I can custom order engines to be sold stock or modified.
The Fx K501 is $370.00
Fx K301r K302R $370.00
I can custom order any of the Reds engines.
The R5R is popular for $250, $300.00 modified.
Wr7 Diamond 2.0 $470.00
Fx K301 review
Fx K501R review
Fx K501R follow up