which would be the best fit for it?

KA20
H22
B18C5
B18C3
B16A2
B18C1
D16Z6
D15 vtec

top is from 3500-500

It all depends how much your willing to spend? If u have deep pockets K20 for sure. If your going to turbo it Again K20 or B18. l love the H22 but its way more work to get the full power out of it, cause u cant do high boost till u bore out the block. For the same price of a B18 Gsr u can get K20 if u look around.

All out:
K20

More Powerful:
B16A

To get it done & over with:
D15B (VTEC)

any B series motor will drop right in AKA GSR, Type R, or LS motor.even the Civic S l B16A motor will fit.the K20 & H22 motor have good power but r far to heavy for the civic & will hurt the speed over the B series motors. l have the GSR motor in a 96 civic & have no complaints over the car except on the high way scince l have the P72 transmission it is geared really low for quick acceleration, so once l hit 60 i'm already at 3,000 RPM so if l go faster it hurts my gas mileage.but l will roast many car on the high way.check out Hassport performance l believe they have a guide that shows u which motors r a direct swap with out new motor mounts & shift linkage.also u may want to upgrade ur motor mounts to handle the power u will put into ur car..my buddy has snapped one & put the motor up into the hood of the car. good luck

just do like a jdm d15b or a d16z6. they both are very easy and only involve little wiring.