can i put a VTEC engine in a 2000 Honda civic lx?

Yes from my point of view you have to main options: the b18 motor personally i think this is the better option its a 1.8 liter motor fuel efficient and still runs great. Or you could go with the K20A which is a 2.0 liter motor little more power but the swap will be a lot harder than the b18. Both motors are vtec motors.
These are the only motors i can think of that would fit. hope i helped