How can I approach transitioning a highly customized 15/09A shops section to Bootstrap 4?
Other than the navigation bar the Price Tapestry template only really uses the layout styles of Foundation so it should be relatively straight forward to convert. If you study the html/* files you'll notice that the responsive layout is achieved through the "row" and "small-x medium-x columns" class definitions and these should have very similar equivalents in Bootstrap so that is essentially what would be involved.
If you were looking to migrate for a particular feature don't forget that there is an extensive UI library for Foundation 5 - check out the "Kitchen Sink" page here for all the various features that you can include;
David, thanks so much! I had no idea where to begin.