Ultra marathons are all about training volume over speed. You need to run a lot of miles in training if you’re going to run a lot of miles on race day. You’ll be using your aerobic energy system which uses fat as fuel, so you need to make sure you train within your aerobic training zone. This means that, for the majority of your runs, you’ll be keeping the pace nice and easy.
While this training plan focuses on covering the miles, if you’re used to doing a weekly speed session and want to continue doing so, you can. Choose which midweek training run is the closest distance to your intended run, and do it there instead.