Turbocharging a ZC, D or B series turbo?

My friend's got a zc swap in his '91 Si hatch and wants to turbocharge it, but I have no clue as to whether he needs to buy a D or B series turbo since is the black-top dohc. Can somebody help me out? What's his compression, and how much boost can he run with stock everything?

is it a DOHC or SOHC, because they have different cr's. If it's a DOHC, it has a compression ratio of 9.6. If it's a SOHC, it has a compression ratio of 9.1. About the turbo issue, i have no clue, but i would like to hear the outcome.

but I have no clue as to whether he needs to buy a D or B series turbo since is the black-top dohc
It's a dohc...

then he has a compression of 9.6

9.1 without Catalytic Converter
9.5 with Catalytic Converter
thats his compression ratio.

My second option was to go the route of a turbo. Even though there was not an actual Turbo kit directly for the ZC (d16a8 - in the U.S. that is) several people had been successful in mating the GReddy Turbo kit for the 92-95 Honda Civic SOHC VTEC engine (D16Z6) to the ZC since the exhaust manifolds were the same. The cost of the GReddy Turbo was about $1500 without an intercooler. Since my plan was only to boost 6psi and I would be using this as a daily driver and needed an efficient system - I decided on the turbo route.
Credit to: http://www.88-crx.com/ZC%20Turbo.htm

How does a catalytic converter change the compression?

I'm not sure that may be wrong, that's what was stated on the site above. I'll do a search and see if i can find out though

yeah, that cat shouldn't have anything to do with the compression ratio

the cat having something to do with compression? that's rediculous!! it's just a part of the exhaust system... compression only has to do with the internals on your engine eg, what pistons you're using... that's my 2 cents