B20z and B20a differences

I have an opprotunity to buy a '90 (I believe... I'll have to check again) Prelude for $100. The owner didn't change the timing belt and it snapped... bending valves. My question is, since it is hard to source the B20z heads, what are the differences in the b20z and b20a? I'm not too keen on the b20z. If they are interchangable, then I can pick up a CR-V head and slap that hoe on there and have a $300-400 Prelude. The car is in relatively good shape, with newer tires and a good interior. I have a Pathfinder, which is an incredibly fun vehicle, but I'm changing careers and I just want a beater that gets good gas milage. Any help would be great. Maybe if I don't get it... someone else might be interested. It is located in South Alabama, about 15 minutes East of Mobile.