Sounds to me like you have a B20 block with a B18 head - not a happy marriage, that would result in pretty high compression, unless the rings were really bad, without much gain in performance. I'd suggest you look for a B20 head and a D cam. You could, of course, go for a B18 block, and if you are anywhere near the upper right-hand corner of the U.S., I'd be glad to give you one. I have a B20 in my PV, and it is a gas, but really more engine than the car was designed for - at over 80 mph, steering gets light and it feels as if the car starts to levitate. In retrospect, I think I would be just as happy with a B18, which is quieter and easier on the fuel consumption. Parts are, perhaps, a little more difficult to find, but not by much. Just one geezer's opinion, others, I'm sure, will differ.
Bob S.