The bottom of the steerer should be entirely inside the crown. I usually leave a MM or two to clean up on the underside.

270mm would be a bit long, but you can tweak it by leaving more showing at the bottom of the crown (measure to fit, add 5-10mm that you can trim off the threaded end later, and trim the non-threaded end).

32mm is a bit low for stack height, the only ones I remember that are near that short are the old ball and race 105 and Sante units, the Ritchey Logic, and maybe a couple of Tange units if you're lucky. I usually use 40mm, which is around what the Ultegra and Dura Ace cartridge units are. Remember, it's easier to use spacers than it is to grow a longer steerer.

Pete