colts fan here. not sure why they changed from a 3-4 to 4-3. the 3-4 is much more effective versus the colts if they have the right personnel. fangio is a horrid d-coordinator. we had him in indy before, so we know.
my guess is that they realized that they just simply don't have the proper personnel to run it, so they're switching instead of drafting players to fit the 3-4.
3-4 defenses do give the colts fits though. the patriots, steelers, chargers, and baltimore have all given the colts problems.
good luck with williams... a decent choice, but probably could have had better value by dealing down, getting dbrickshaw and extra picks to bolster the o-line. I hear people on here saying that DE pressures lead to turnovers which lead to better field position. yes, true, but so does keeping your QB upright and keeping pressure off of him. it minimizes offensive turnovers and helps keep drives alive instead of taking sacks and killing drives.