SOHC heads and blocks don't mix with DOHC heads and blocks.
There is a possible exception, but that involves engines from 87 and earlier. And actually, I only heard of one person ever doing that, so maybe he was lying. It was a DOHC D16A1 head on a D15A3 block.
I think you should use a Y8 if you can find one, but it's a lot easier to find a Z6. People say the Y8 will give too high compression, but I think you will be all set if you just use the regular pistons. The Y8 is nice because everything pretty much bolts up to the A6 block, and if you stay OBD0 your dizzy will bolt up too. Also, since they came off newer cars, they are generally younger.
I'm running a Y8 head, Dren and Tiersin have Z6s. There are a couple of other people on here waiting to do their swaps too, we have a good support group for when (not if haha!) it doesn't work.
Well omg i got a y8 already its in my civic and i was just wondering if it was possible for the a6 to go into my civic 97 ex that way i wouldnt have to buy another head? OMG if any1 wants to come and help me on my crx i will pay you 30 dollars to come to richmond va plz i need some1 that will actually give me a hand because alot work on my car would be easyier with another hand. And im really gonna pay you to take the head off my civic and put it on my crx i dont no how to do that stuff. but willing to learn.
Don't tear apart your other car for the head. You can find a good SOHC VTEC head for sale and keep the Civic on the road so you will have something to drive when you're working on the rex. Chances are you would have problems getting the mini-me going, and then you would have nothing to drive, or at the very least you would have a slow crappy civic that you wouldn't want to drive.
An H22 is a rather involved swap, and certainly more expensive than a B16, which is practically bolt-in. Both of those options are also considerably more than just a head swap. We all have big ambitions, but sometimes we need to work within our own budget. I'm sure jfish would be into bigger and better things if he could afford it.