Was wondering if I can install a 400 crank and piston into a 455.  

No, the 455 boe is already .030" larger than a stock 400 piston and the main journals in a 455 are 3.25" diameter whereas the 400 uses a 3" main. A popular destroke of a 455 is to use a 428 crank, also 3.25" mains, to get 440 cubic inches. There are parts available to turn a 400 (bored .030" over) into a 455 using a custom 3" main 4.21 stroke crank from Ohio Crankshaft, stock rods and stock size 455 pistons. Also available are 3" main, 4.25" stroke cranks that require specific aftermarket rods and pistons for 461 cubes out of a 400 block, I believe there are several suppliers for this combo.
Steve