Fueling for a Z2 marathon

Hey! I will be attempting to run the Boston Marathon, but I’ve been battling an injury for the last month and unable to complete my planned training in the time (no long runs, all short runs painful.) To this point, doctors still think I can trot the marathon because it’s Boston and likely my only chance to run it. This means I’m running at a pace about double my race pace with my HR in zone 2 most of the time and very relaxed!

That being said! I’m curious if you have any insight on race day fueling for a race where you’re going to distance but no where near lactic threshold when pacing. I know I’ll need to fuel throughout, but the type of fuel feels like it should be a different source from my normal gu/energy chew tactic with different timing?? Any insight would help!