Well, think about what you just said. 205 v. 155. The STOCK GA16i puts out 90hp, probably closer to like 75-80whp. Just doubling that will give you some AWESOME power to weight ratios. I mean, think of the Honda guys. Stock a B16 puts out like 140-160hp (I think, don't quoite those numbers). Put that motor into an 88-91 hatch and you've got a mid 14 second car (down from 18's stock). Now, you boost it, making it like 200-250hp, and you're EASILY into the 13's, maybe high 12's.
The KA24DE motor puts out close to 150hp I think. now, that'll be almost double to the wheels what the stock GA16i puts out. The powerband is right around 3600-6300 I believe, and in SCCA events, you're never gonna get higher than 3rd, MAYBE 4th, so you'll stay in that powerband. Also, don't forget you can strip down the B12 and probably get her below 2000 lbs. A sub 2000lb car w/ 160hp would be KICK ASS!
Now, for SCCA, don't they have rules for motor swaps and such? Or is that just different class specifications.