I dont think you should blow your motor, your block is a great foundation.
I like the Idea of a lighter weight K memeber as well, although my reason is for a lighter weight and better balanced car for the twisties.
I disagree with the notion of nitrous however, its pricey to build these motors N/A in the first place (so you'd sacrifice constant power), and with an F/I set up instead, youd beat up on honda's whenever you wanted, meet your low 12's - high 11 goals, and still be very streetable.
I know its a random tangent because you were just asking about a k-member, but the best option I've heard of for these cars is forged rods and pistons (the factory crank is fine) and boosting them to whatever you want. Granted thats one sentence to explain a big process but its essentially the theory. Nitrous may work for you, but thats just my thoughts (i favor twisties over straight line and would prefer a higher torque curve all the time than relying on a bottle, so I'm biased)