Not sure what exact parts he used, but the A1 upgrades included the larger turret bustle stowage basket, guards around the driver’s and commander’s periscopes, an NBC system for the crew (not the troops in the back), side firing ports deleted (on M3A1 only), and some other minor changes. All of the extra parts are in the Tamiya M2A2 kit.
This is all laid out in the M2/M3 Bradley Reference thread.