Whats the deal with the KB 243's, good or not?

It's like anything, pick the right part for the application. They are excellent street performance pistons with proper ring gaps. I have ran them to 7000 rpm for thousands of laps in a oval track engine with zero failure. But for forced induction or nitrous, I'd be looking into a forged piston.
Good to hear they hold up to that punishment, thanks.