Embodiments can provide automated matching of items to cart items and generation and rendering of customized template blocks, such that the appearance of the template blocks is adaptive, with remote configuration and optimization at one or more stages of a process. An integration plugin can enable websites to present additional items that are associated with an item displayed on a web page. The integration plugin can be compatible with many websites, be plug-and-play, quickly installed, and not require significant programming effort from the website. Embodiments can provide integration into the web site leading to increased conversion rates. Embodiments can provide information from a first item for additional items without additional data entry. Embodiments can provide real-time performance tracking for monitoring and optimization. Embodiments can provide composite user interfaces to manage item matching, performance tracking, and configuration.