"The second kind of ZC is the same as the U.S. Si and is SOHC and came on lower Integra
models in Japan. It seems to be very similar to the 1986-1989 Integra engine setup.
So basically they bolt into the second generation Integra and would be the same as an Si."

Took this quote from an old ZC site from back in the day. Google owns. So basically it is a d16a6 with a block casting to bolt into 1g integras and 1g crx's. So a vtec head would fit but it won't bolt into a 4g civic.....but I think I remembered hearing about sohc zc that fit 4G. Maybe a low model JDM 88 civic. SOHC vtec head should fit this motor.