If you can find the pistons, they're 1.928 ch which is a bit taller than the kb240. The 440 pistons are just cast not hyperutectic.
Chances are your 400 will need to be decked quite a bit to get squared up. Alot of blocks end up around a 9.70 deck height.
The 240s would be sitting around .030 under the deck. That will help a bit. With pistons that far below you won't have to worry about valve clearance. I assume you won't be running any moderate-big cam
(Otherwise the car will be a turd).
