carb for mini blower

I just posted this in the fuel section and realized it may need to be in this section. Anyway, I am wondering about carb size, and type that mounts on top of one of those little superchargers like the weiand or BnM. I just got it off of ebay and have'nt ever had a supercharger before, but I've done a little reading on the subject. What I've come up with is it needs to be a boost carb and a boost ref fuel regulator. Size and type alludes me.
It's going on a 318 with a 4 inch crank rods and forged pistons. The guys says it's a 174 but he's not sure and neither am I. I thought it looked like one of those 144's but I am not sure, I don't know how to tell the differance. Anyway he said he had it on a 340 with a 850 carb but who knows for sure. He said the pully set up gave him 5 lbs of boost, which would work for me right now. I did some checking on the web with these little blowers, what I found was 9.5 comp 5 lbs boost will work. I guess we'll see, I still have'nt got a dial back igniton box yet but have one in the plan, just not yet.
Theres a return policy if it does'nt perform as he says it will but I think it's like 14 days, so i gotta get this thing on and running to try it out. Any input would help. Thanks