I've some talk about an f20 (s2k) motor fitting in a civic with the right tranny. Is that possible without a lot of custum modifications?

 

You could make it fit with a K-series tranny, custom mounts, custom axles, custom tranny adapter plate and alot of wiring
It can be done. But it'd be alot easier/cheaper/better to put in a K20a2.

 

Why would it be better if the s2000 motor is a lot better all around and cheaper to buy itself than the k20?

 

anything is possible. It just getting an adapter plate to be made for it to work with a fwd tranny. Maybe whoever makes the b series tranny to h series block adapter plate should think about the a k series tranny to f20 block. It's all about $$$