No, I can't agree here, you'll pay $1000 extra for 10 hp? You can do that w/ a headgasket change. ANY B series tranny will work w/ ANY Bseries engine. Only drawback to an SiR tranny (if you commute that is) is I am at 5k rpm at 80 mph. For the street it is an AWSOME tranny. Just FYI I get 26 mpg and drive an hour back and forth to my job. I drive HARD from time to time and still get that good of gas mileage. I say, be simple. If it's you first swap, do a 1st gen B16A. Very simple.
You want complicating, order an SiR II longblock, a Bseries cable tranny, reharness the engine w/ your Si harness (you'll have to do that anyway) but cut the dist plug and resolder a different plug from your Si dist., should I keep going? If you ask me a lot of trouble for 10 hp. Like I said, run a thinner headgasket and newer B16A cams and you 10 + hp has been made up.
1st gen B16A cams are ass.