Dart's new LS Next line of blocks feature a handful of improvements over the GM blocks, but the unique main cap design requires it's own style of windage tray. The kit comes with all the hardware required to mount the tray to the block.
In our experience, some nipping and tucking is required to get certain oil pump pickups mounted to the caps. Most commonly it involves reshaping and/or extending the pickup's mounting tab. Another consideration to keep in mind is the dipstick. The LS Next SHP has a dipstick provision in the side of the block. To use it (rather than either going without a dipstick or installing one in the pan directly) you need to cut a hole in the windage tray.
If your pan has a windage tray, we would suggest not using this one.
Alternatively, we offer custom made pans for the LS Next blocks without side skirts. Our data shows a 5% HP gain between an unskirted block with the custom pan with generous kickouts and baffling vs the skirted block, a windage tray and a GM pan. Some custom pan pictures are available here and a version is shown in the graphic below. The pan can be ordered with provisioning for the passenger side AC compressor and the driver side alternator mount if required. They range from $950-$1,050 depending on options.